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Reference Resource:

SI - The Metrics International System of Units

 

Last Updated:

Symbols | Length | Area |  Volume | Force | Pressure | Mass | Temperature | Power | Useful Conversions | Pavement |

Pavement marking | Sheet metal | Reinforcing Steel | Wire | Sieve | Hard | Trades | Pipe | Structural Plate

The International System of Units (SI) is a modernized version of the metric system established by international agreement. The metric system of measurement was developed during the French Revolution and was first promoted in the U.S. by Thomas Jefferson. Its use was legalized in the U.S. in 1866. In 1902, proposed congressional legislation requiring the U.S. Government to use the metric system exclusively was defeated by a single vote.

SI provides a logical and interconnected framework for all measurements in science, industry, and commerce. The metric system is much simpler to use than the existing English system since all its units of measurement are divisible by 10.

Conversion Factors

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The following list provides the conversion relationship between U.S. customary units and SI (International System ) units. The proper conversion procedure is to multiply the specified value on the left (primarily U.S. customary values) by the conversion factor exactly as given below and then round to the appropriate number of significant digits desired. For example, to convert 11.4 ft to meters: 11.4 X 0.3048 = 3.47472, which rounds to 3.47 meters. Do not round either value before performing the multiplication, as accuracy would be reduced. A complete guide to the SI system and its use can be found in ASTM E 380, Metric Practice.


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Conversion Symbols

The prefixes and symbols listed below are commonly used to form names and symbols of the decimal multiples and sub multiples of the SI units.


                        INTERIM UNITS OF MEASURE
                  As suggested by Federal Standard 376B
                            January 27, 1993
 
   AS USED IN THE                                METRIC
 STANDARD ITEM TABLE                           EQUIVALENT
ACRE                                      hectare (ha)
CUBIC FOOT                                cubic meter (m3)
CUBIC YARD                                cubic meter (m3)
GALLON/MGALLON                            liter (L), cubic meter (m3)
HUNDRED                                   Hundred for traffic buttons
HUNDRED WEIGHT                            kilogram (kg)
LINEAR FOOT                               meter (m)
MBOARD FEET                               cubic meter (m3)
MILE                                      kilometer (km)
NAUTICAL MILE                             Nautical Mile
POUND                                     kilogram (kg) for mass                                
                                          newton (N) for force
SQUARE FOOT                               square meter (m2)
SQUARE YARD                               square meter (m2)
TON                                       tonne (t)
 

                    
 
UNITS OF MEASUREMENT                             METRIC 
USED IN SPECIAL PROVISIONS                     EQUIVALENT
AND GENERAL SPECIAL PROVISIONS
--------------------------------------------------------------------------------
GAGE;GAUGE             METAL THICKNESS         gage (mm)
FAHRENHEIT             TEMPERATURE             kelvin (K) or degree Celsius (C)
FATHOM                 WATER DEPTH             meter (m)
FOOT/LBS               TORQUE                  newton-meter (N-m)
LBS/SQ. IN             PRESSURES               kilopascal (kPa)
                                               megapascal (MPa)
                                               (if very large number)
LBS/SQ. FT                                     kilopascal (kPa)
LBS/SQ YD                                      kilopascal (kPa)
INCH                   LINEAR                  millimeter (mm)
KIPS;KSI               TENSION                 kilopascal (kPa) or
                                               megapascal (MPa)
LBS/ACRE               EROSION CONTROL         kilograms/hectare
LBS/CU. FT.            DENSITY                 kilogram per cubic meter (kg/m3)
MIL                    THICKNESS               micrometer (um)
FT. LBS./SEC.          HORSE POWER             watt (W)
 

UNITS OF MEASUREMENTS USED                       METRIC
ON CONTRACT PLANS                              EQUIVALENT
     DEGREES/BEARINGS                          No change for surveying.
 
     STATIONING                                1,000 meters = 1 station  
 
 
     MILEPOSTS                                 This one is still under review
                                               as mileposts are part of the signing
                                               issue.  Use mileposts for now, but also
                                               state kilometerposts.
 
 
     ELEVATIONS                                meter (m)
 

UNITS OF MEASUREMENT USED IN                     METRIC
COMMERCIAL STANDARDS                           EQUIVALENT
     GALS/HR or MIN (PUMPS)                    liters per second (L/s)
 
     500 GALLON TANKS                          cubic meter (m3) but it could
                                               also possibly be in liter (L)
 
     55 GALLON DRUMS                           cubic meter (m3) or liter (L)
                                               for liquid
 
     94 LBS/SACK (CEMENT)                      kilogram (kg)
 
     DIAMETER OF REINFORCING STEEL             millimeter (mm)
 
     LBS/FT OF REINFORCING STEEL               kilogram per meter (kg/m)
 
     BUSHEL                                    cubic meter (m3)

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Length Conversion Factors

Length
To convert from        to                     multiply by    
mile (US Statute)      kilometer (km)         1.609347       
inch (in)              millimeter (mm)        25.4  * 
inch (in)              centimeter (cm)        2.54 *  
inch (in)              meter (m)              0.0254 *       
foot (ft)              meter (m)              0.3048 *       
yard (yd)              meter (m)              0.9144 *

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Area Conversion Factors

Area
To convert from		to			multiply by
square foot (sq ft) square meter (sq m) 0.09290304 E square inch (sq in) square meter (sq m) 0.00064516 E square yard (sq yd) square meter (sq m) 0.83612736 E acre (ac) hectare (ha) 0.4047

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Volume Conversion Factors

Volume
To convert from		to			multiply by
cubic inch (cu in) cubic meter (cu m)	0.00001639	
cubic foot (cu ft)	cubic meter (cu m)	0.02831685	
cubic yard (cu yd)	cubic meter (cu m)	0.7645549	
gallon (gal)		liter			4.546	
Canada liquid	
gallon (gal)		cubic meter (cu m)	0.004546	
Canada liquid	
gallon (gal)		liter			3.7854118	
U.S. liquid**	
gallon (gal)		cubic meter (cu m)	0.00378541	
U.S. liquid	
fluid ounce (fl oz)	milliliters (ml)	29.57353	
fluid ounce (fl oz)	cubic meter (cu m)	0.00002957
                        

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Force Conversion Factors

Force
To convert from		to			multiply by 
kip (1000 lb) kilogram (kg) 453.6 kip (1000 lb) newton (N) 4,448.222 pound (lb) kilogram (kg) 0.4535924 avoirdupois pound (lb) newton (N) 4.448222

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Pressure or Stress Conversion Factors

Pressure or stress
        kip per square        megapascal (MPa)          6.894757
          inch (ksi)
        pound per             kilogram per              4.8824
         square foot (psf)      square meter (kg/sq m)
        pound per square      pascal (Pa)               47.88
          foot (psf)
        pound per square      pascal (Pa)               6,894.757
          inch (psi)
        pound per square      megapascal (MPa)          0.00689476
          inch (psi)

 


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Mass Conversion Factors

Mass (weight)
        pound (lb)            kilogram (kg)             0.4535924
          avoirdupois
        ton, 2000 lb          kilogram (kg)             907.1848
        grain                 kilogram (kg)             0.0000648
Mass (weight) per length        kip per linear        kilogram per meter (kg/m) 0.001488
          foot (klf)         
        pound per linear      kilogram per meter (kg/m) 1.488
          foot (plf)         
Mass per volume (density) 
        pound per cubic       kilogram per cubic        16.01846
          foot (pcf)           meter (kg/cu m)
        pound per cubic       kilogram per cubic        0.5933
          yard (lb/cu yd)      meter (kg/cu m)
                        

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Temperature Conversion Factors

Temperature
        degree Fahrenheit (F)     degree Celsius (C)        	tc=(tF-32)/1.8
        degree Fahrenheit (F)     kelvin (K)		    	tk = (tF+459.7)/1.8
        kelvin (K)	          degree Celsius (C)        	tc=tk-273.15
Energy and heat        British thermal           joule (J)                 	1055.056
         unit(Btu)
        calorie (cal)             joule (J)                 	4.1868E
        Btu/degree       	  F x hr x ft2  W/m2 - degree K	5.678263
        kilowatt-hour (kwh)       joule (J)                 	3,600,000E
        British thermal           calories per gram         	0.55556
         unit per pound (Btu/lb)    (cal/g)
        British thermal unit      watt (W)                  	0.2930711
         per hour (Btu/hr)
                        

                

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Power Conversion Factors

Power horsepower (hp) watt (W) 745.6999 E (550 ft-lb/sec) Velocity mile per hour (mph) kilometer per hour(km/hr) 1.60934 mile per hour (mph) meter per second (m/s) 0.44704 Permeability darcy centimeter per 0.000968 second (cm/sec) feet per day (ft/day) centimeter per 0.000352 second (cm/sec) ---------- *indicates that the factor given is exact. **One U.S. gallon equals 0.8327 Canadian gallon. t--A pascal equals 1.000 newton per square meter. Note: One U.S. gallon of water weighs 8.34 pounds (U.S.) at 60 degrees F. One cubic foot of water weighs 62.4 pounds (U.S.). One milliliter of water has a mass of 1 gram and has a volume of one cubic centimeter. One U.S. bag of cement weighs 94 lbs.

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More Useful Conversion Factors

USEFUL CONVERSION FACTORS

QuantityFrom English           To Metric             Multiply
                      Units                  Units                 by*

Lengthmile                    km                 1.609347
                      yard                    m                  0.9144**
                      foot                    m                  0.3048**
                      inch                    mm                 25.40**

Areasquare mile                km 2               2.590
                      acre                    m 2                4047
                      acre                  hectare              0.4047
                   square yard                m 2                0.8361
                   square foot                m 2                0.092 90
                   square inch                mm 2               645.2

Volumeacre foot                 m 3                1 233
                   cubic yard                 m 3                0.7646
                   cubic foot                 m 3                0.028 32
                   cubic foot            L (1000 cm 3)           28.32
                 100 board feet               m 3                0.2360
                     gallon              L (1000 cm 3)           3.785

Mass                   lb                      kg                0.4536
                  kip (1000 lb)            metric ton (1000kg)   0.4536

Mass/unit length       plf                    kg/m               1.488

Mass/unit area         psf                   kg/m 2              4.882

Mass density           pcf                   kg/m 3              16.02

Force                  lb                       N                4.448
                       kip                     kN                4.448

Force/unit length      plf                     N/m               14.59
                       klf                    kN/m               14.59

Pressure, stress,                         
modules of                                  
elasticity             psf                     Pa                47.88
                       ksf                    kPa                47.88
                       psi                    kPa                6.895
                       ksi                    MPa                6.895

Bending moment,        ft-lb                  N . m               1.356
torque, moment of forceft-kip                kN . m               1.356
---------------------
  * 4 significant digits
  **denotes exact conversion
                        

USEFUL CONVERSION FACTORS

Quantity            From English Units    To Metric Units    Multiply by*
Moment of mass lb . ft kg . m 0.1383 Moment of inertia lb . ft2 kg . m 2 0.042 14 Second moment of area in4 mm4 416 200 Section modulus in3 mm3 16 390 Power ton (refrig) kW 3.517 Btu/s kW 1.054 hp (electric) W 745.7 Btu/h W 0.2931 Volume rate of flow ft 3/s m 3/s 0.028 32 cfm m 3/s 0.000 471 9 cfm L/s 0.4719 mgd m 3/s 0.0438 Velocity, speed ft/s m/s **0.3048 Acceleration f/s 2 m/s 2 0.3048 Momentum lb . ft/sec kg . m/s 0.1383 Angular momentum lb . ft 2/s kg . m 2/s 0.042 14 Plane Angle degree rad 0.017 45 mrad 17.45 --------------------------------- * 4 significant digits **denotes exact conversion

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Pavement Conversion Factors

METRIC CONVERSION--PAVEMENTS
ROADWAY   DIMENSIONS  BRIDGE HT.        PCCP Thickness'     RESILIENT MODULUS
          ft   m        ft   m          (inches)(mm)            psi      MPa
Lane      12   3.6    14.5  4.4            9    225            3,000     21
Shoulder  4    1.2    16.0  4.9           10    250            4,000     28
          10   3.0                        11    275            5,000     34
                                          12    300           10,000     69
                                                              12,000     83
                                                              15,000    103
                                                              20,000    138
TYPICAL DENSITY VALUES          AXLE LOADS         TIRE LOADS (per tire width)
         pcf     kg/m 2        lbs      kN          lbs/inch     kg/mm
PCCP 150 2403 18,000 80 500 9 ACP 137/0.10' 2439 depth TYPICAL QUANTITIES Asphalt Concrete Paving Quantities (metric tons/kilometer) Depth of Pavement (ft) 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 (mm) 30 45 60 75 90 105 120 135 150 165 180 195 210 225 ============================================================================================= Width of| Pavement| (ft) (M) | Metric tons per kilometer 4 1.2 | 88 132 176 219 263 307 351 395 439 483 527 571 614 658 6 1.8 | 132 198 263 329 395 461 527 593 658 724 790 856 922 988 8 2.4 | 176 263 351 439 527 614 702 790 878 966 1,053 1,141 1,229 1,317 10 3.0 | 219 329 439 549 658 768 878 988 1,097 1,207 1,317 1,427 1,536 1,646 11 3.3 | 241 362 483 604 724 845 966 1,086 1,207 1,328 1,448 1,569 1,690 1,811 12 3.6 | 263 395 527 658 790 922 1,053 1,185 1,317 1,448 1,580 1,712 1,843 1,975 22 6.6 | 483 724 966 1,207 1,448 1,690 1,931 2,173 2,414 2,655 2,897 3,138 3,380 3,621 24 7.2 | 527 790 1,053 1,317 1,580 1,843 2,107 2,370 2,634 2,897 3,160 3,424 3,687 3,950 --------------------------------------------------------------------------------------------- Based on 2439 kg/m 3 ; 30 mm compacted depth = 73.17 kg/m 2

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Pavement Marking Conversion Chart

---------------------------------------------------------------------------------------------
|  Wet Material Thickness    |      Edge Line Coverage      |      Area Coverage            |
|----------------------------|------------------------------|-------------------------------|
|  English      | Metric     | English | Met./Eng.| Metric  | English | Met./Eng.| Metric   |
| mils (0.001") | mm(0.001M) |  Ft/gal | M/gal    | M/Liter |  SF/gal | SM/gal   | SM/Liter | 
|===============|============|=========|==========|=========|=========|==========|==========|
|      1.0      |    0.025   |  4832   |  1473    |  393.7  |  1611   |  150     |  39.37   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     10.0      |    0.254   |   483   |   147    |   39.4  |   161   |   15     |   3.94   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     15.0      |    0.381   |   322   |    98.2  |   26.2  |   107   |   10     |   2.62   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     19.7      |    0.500   |   245   |    74.8  |   20.0  |    82   |    7.6   |   2.00   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     20.0      |    0.508   |   242   |    73.6  |   19.7  |    81   |    7.5   |   1.97   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     25.0      |    0.635   |   193   |    58.9  |   15.7  |    64   |    6.0   |   1.57   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     30.0      |    0.762   |   161   |    49.1  |   13.1  |    54   |    5.0   |   1.31   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     35.0      |    0.889   |   138   |    42.1  |   11.2  |    46   |    4.3   |   1.12   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     39.4      |    1.000   |   123   |    37.4  |   10.0  |    41   |    3.8   |   1.00   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     40.0      |    1.016   |   121   |    36.8  |    9.8  |    40   |    3.7   |   0.98   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     45.0      |    1.143   |   107   |    32.7  |    8.7  |    36   |    3.3   |   0.87   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     49.2      |    1.250   |    98   |    29.9  |    8.0  |    33   |    3.0   |   0.80   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     50.0      |    1.270   |    97   |    29.5  |    7.9  |    32   |    3.0   |   0.79   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     59.1      |    1.500   |    82   |    24.9  |    6.7  |    27   |    2.5   |   0.67   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     60.0      |    1.524   |    81   |    24.5  |    6.6  |    27   |    2.5   |   0.66   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     78.7      |    2.000   |    61   |    18.7  |    5.0  |    20   |    1.9   |   0.50   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     88.6      |    2.250   |    55   |    16.6  |    4.4  |    18   |    1.7   |   0.44   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     90.0      |    2.286   |    54   |    16.4  |    4.4  |    18   |    1.7   |   0.44   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|     98.4      |    2.500   |    49   |    15.0  |    4.0  |    16   |    1.5   |   0.40   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    100.0      |    2.540   |    48   |    14.7  |    3.9  |    16   |    1.5   |   0.39   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    118.1      |    3.000   |    41   |    12.5  |    3.3  |    14   |    1.3   |   0.33   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    120.0      |    3.048   |    40   |    12.3  |    3.3  |    13   |    1.2   |   0.33   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    236.2      |    6.000   |    20   |     6.2  |    1.7  |     7   |    0.6   |   0.17   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    250.0      |    6.350   |    19   |     5.9  |    1.6  |     6   |    0.6   |   0.16   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    255.9      |    6.500   |    19   |     5.8  |    1.5  |     6   |    0.6   |   0.15   |
|---------------|------------|---------|----------|---------|---------|----------|----------|
|    260.0      |    6.604   |    19   |     5.7  |    1.5  |     6   |    0.6   |   0.15   |
|-------------------------------------------------------------------------------------------|
| WDB 4.22.97                                                                               |
=============================================================================================

                        

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Sheet Metal Conversion Factors

SHEET METAL Most specification references use gage number followed by the decimal inch thickness. Example: 22 gage (0.034 inch) Metric specifications use the absolute mm thickness. It is not the intent of this guidance to change the thickness of currently used sheeting. The following chart may be used to specify sheet metal. The thickness under "Specify" is thinner than the actual gage thickness, since specifications give minimum thickness.

      Gage         Inch            Exact         Specify          Percent Thinner
                                   (mm)           (mm)             Than "Exact"
                                                                       Value
            
       32         0.0134          0.3404           0.34                 0.1
       30         0.0157          0.3988           0.39                 2.2
       28         0.0187          0.4750           0.47                 1.1
       26         0.0217          0.5512           0.55                 0.2
       24         0.0276          0.7010           0.70                 0.1
       22         0.0336          0.8534           0.85                 0.4
       20         0.0396          1.0058           1.0                  0.6
       18         0.0516          1.3106           1.3                  0.8
       16         0.0635          1.6129           1.6                  0.8
       14         0.0785          1.9939           1.9                  4.7
       12         0.1084          2.7534           2.7                  1.9
       10         0.1382          3.5103           3.5                  0.3
        8         0.1681          4.2697           4.2                  1.6
                        

This schedule was developed since no existing material was found to clearly identify existing sheeting in metric units. Until a more efficient method is developed to address this issue, specifiers may wish to retain the gage number in specifications, and couple this with a rounded mm size in parenthesis.


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Reinforcing Steel Conversion Factors

REINFORCING STEEL

The following table shows the current U.S. customary rebar sizes in relationship to the respective diameters and cross-sectional areas.

                    Customary English              Metric
                         System                  Equivalent
                  ---------------------------------------------
U. S. Customary   Diameter      Area         Diameter     Area
  Designation       (in.)      (in 2)          (mm)      (mm 2)
       #3          0.375        0.11            9.5         71
       #4          0.500        0.20           12.7        127
       #5          0.625        0.31           15.9        198
       #6          0.750        0.44           19.1        285
       #7          0.875        0.60           22.2        388
       #8          1.000        0.79           25.4        507
       #9          1.125        1.00           28.6        641
       #10         1.270        1.27           32.3        817
       #11         1.410        1.56           35.8       1007
       #14         1.693        2.25           43.0       1452
       #18         2.257        4.00           57.3       2581
                        

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Wire Conversion Factors

SEVEN-WIRE, UNCOATED STRAND FOR PRESTRESSED CONCRETE STRUCTURES The prestressing industry again uses the soft conversion for all dimensional units of prestressing wire. This soft conversion is utilized worldwide and a copy of the equivalent physical properties for Grade 270 low-relaxation strand, as provided by Florida Wire and Cable Company, is provided below:

              270 GRADE LOW-RELAXATION ASTM A-416
            
---------------------------------------------------------------------------
Nominal Strand       Minimum Strength                 Area      Diameter
     (mm)       (in.)      (kN)       (lb.)            (mm 2)    (in 2)

      10        (3/8)     102.3     (23,000)            54.8    (0.085)
      11        (7/16)    137.9     (31,000)            74.2    (0.115)
      12        (15/32)   160.1     (36,000)            85.8    (0.133)
      13        (1/2)     183.7     (41,300)            98.7    (0.153)
      14        (9/16)    230.0     (51,700)           123.9    (0.192)
      15        (0.600)   260.6     (58,600)           140.0    (0.217)
---------------------------------------------------------------------------
                        

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Sieve Conversion Factors

SIEVES

Sieve Designation (W)
            
--------------------------------------------------------------------------------------------
Nominal    Permissible Variation    Intermediate     Maximum    Nominal
Standard Alternative Sieve       of Average Opening       Tolerance    Individual     Wire
                    Opening      from the Standard           (x)        Opening     Diameter
                     (in.)       Sieve Designation                         (x)        (mm)
                                             (y)                                                
                                            + or 
-------------------------------------------------------------------------------------------
125 mm        5 in.          5             3.70 mm         130.0 mm       130.9 mm     8.00
106 mm       4.24 in.       4.24           3.20 mm         110.2 mm       111.1 mm     6.40
100 mm        4 in.          4             3.00 mm         104.0 mm       104.8 mm     6.30
 90 mm      3 1/2 in.       3.5            2.70 mm          93.6 mm        94.4 mm     6.08
 75 mm        3 in.          3             2.20 mm          78.1 mm        78.7 mm     5.80
 63 mm      2 1/2 in.       2.5            1.90 mm          65.6 mm        66.2 mm     5.50
 53 mm       2.12 in.       2.12           1.60 mm          55.2 mm        55.7 mm     5.15
 50 mm        2 in.          2             1.50 mm          52.1 mm        52.6 mm     5.05
 45 mm      1 3/4 in.       1.75           1.40 mm          46.9 mm        47.4 mm     4.85
37.5 mm     1 1/2 in.       1.5            1.10 mm          39.1 mm        39.5 mm     4.59
31.5 mm     1 1/4 in.       1.25           1.00 mm          32.9 mm        33.2 mm     4.23
26.5 mm      1.06 in.       1.06           0.80 mm          27.7 mm        28.0 mm     3.90
25.0 mm       1 in.          1             0.80 mm          26.1 mm        26.4 mm     3.80
22.4 mm                     0.875          0.70 mm          23.4 mm        23.7 mm     3.50
19.0 mm       3/4 in.       0.750          0.60 mm          19.9 mm        20.1 mm     3.30
16.0 mm                     0.625          0.50 mm          16.7 mm        17.0 mm     3.00
13.2 mm     0.530 in.       0.530          0.41 mm         13.83 mm       14.05 mm     2.75
12.5 mm       1/2 in.       0.500          0.39 mm         13.10 mm       13.31 mm     2.67
11.2 mm      7/16 in.       0.438          0.35 mm         11.75 mm       11.94 mm     2.45
9.50 mm                     0.375          0.30 mm          9.97 mm       10.16 mm     2.27
8.00 mm      5/16 in.       0.312          0.25 mm          8.41 mm        8.58 mm     2.07
6.70 mm     0.265 in.       0.265          0.21 mm          7.05 mm        7.20 mm     1.87
6.30 mm       1/4 in.       0.250          0.20 mm          6.64 mm        6.78 mm     1.82
5.60 mm     No. 3 1/2       0.223          0.18 mm          5.90 mm        6.04 mm     1.68
4.75 mm       No. 4         0.187          0.15 mm          5.02 mm        5.14 mm     1.54
4.00 mm       No. 5         0.157          0.13 mm          4.23 mm        4 35 mm     1.37
3.35 mm       No. 6         0.132          0.11 mm          3.55 mm        3.66 mm     1.23
2.80 mm       No. 7         0.11          0.095 mm         2.975 mm       3.070 mm     1.10
2.36 mm       No. 8         0.0937        0.080 mm         2.515 mm       2.600 mm     1.00
2.00 mm       No. 10        0.0787        0.070 mm         2.135 mm       2.215 mm     0.900
1.70 mm       No. 12        0.0661        0.060 mm         1.820 mm       1.890 mm     0.810
1.40 mm       No. 14        0.0555        0.050 mm         1.505 mm       1.565 mm     0.725
1.18 mm       No. 16        0.0469        0.045 mm         1.270 mm       1.330 mm     0.650
1.00 mm       No. 18        0.0394        0.040 mm         1.080 mm       1.135 mm     0.580
0.850 mm      No. 20        0.0331        0.035 mm         0.925 mm       0.970 mm     0.510
0.710 mm      No. 25        0.0278        0.030 mm         0.775 mm       0.815 mm     0.450
0.600 mm      No. 30        0.0234        0.025 mm         0.660 mm       0.695 mm     0.390
0.500 mm      No. 35        0.0197        0.020 mm         0.550 mm       0.585 mm     0.340
0.425 mm      No. 40        0.0165        0.019 mm         0.471 mm       0.502 mm     0.290
0.355 mm      No. 45        0.0139        0.016 mm         0.396 mm       0.425 mm     0.247
0.300 mm      No. 50        0.0117        0.014 mm         0.337 mm       0.363 mm     0.215
0.250 mm      No. 60        0.0098        0.012 mm         0.283 mm       0.306 mm     0.180
0.212 mm      No. 70        0.0083        0.010 mm         0.242 mm       0.263 mm     0.152
0.180 mm      No. 80        0.0070        0.009 mm         0.207 mm       0.227 mm     0.131
0.150 mm      No. 100       0.0059        0.008 mm         0.174 mm       0.192 mm     0.110
0.125 mm      No. 120       0.0049        0.007 mm         0.147 mm       0.163 mm     0.091
0.106 mm      No. 140       0.0041        0.006 mm         0.126 mm       0.141 mm     0.076
0.090 mm      No. 170       0.0035        0.005 mm         0.108 mm       0.122 mm     0.064
0.075 mm      No. 200       0.0029        0.005 mm         0.091 mm       0.103 mm     0.053
0.063 mm      No. 230       0.0025        0.004 mm         0.077 mm       0.089 mm     0.044
0.053 mm      No. 270       0.0021        0.004 mm         0.066 mm       0.076 mm     0.037
0.045 mm      No. 325       0.0017        0.003 mm         0.057 mm       0.066 mm     0.030
0.038 mm      No. 400       0.0015        0.003 mm         0.048 mm       0.057 mm     0.025
0.032 mm      No. 450       0.0012        0.003 mm         0.042 mm       0.050 mm     0.028
0.025 mm      No. 500       0.0010        0.003 mm         0.034 mm       0.041 mm     0.025
0.020 mm      No. 635       0.0008        0.003 mm         0.029 mm       0.035 mm     0.020
                        

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Hard Conversions for Construction Materials

                               HARD CONVERSION FOR CONSTRUCTION MATERIALS
Structural Steel, M270

              Min. Tensile Strength       Min. Yield Strength             Min. Yield Strength
   Grade              (MPa)                      (MPa)                           (ksi)
---------------------------------------------------------------------------------------------
    36                 400                         250                            36
    50                 450                         345                            50
    50W                485                         345                            50
    70W                620                         480                            70
-------------------------------------------------------------------------------------------
                               Reinforcing Bars, M31M

       Grade                                   Tensile and Yield Strengths
  Metric    English          Tensile Strength      Min. Yield Strength    Min. Yield Strength
   Value     Value                (MPa)                   (MPa)                   (ksi)
----------------------------------------------------------------------------------------------
    300       40                   500                     300                     40
    400       60                   600                     400                     60
---------------------------------------------------------------------------------------------
                               Common Concrete Strengths (f'c)
-----------------------------------------------------------------------
Metric  (MPa)      20        28        35       43       48       55
English  (psi)    3000      4000      5000     6000     7000     8000
-----------------------------------------------------------------------
Coefficient of Thermal Expansion

            Metric  Value     English Value
--------------------------------------------
Steel        0.0000117/oC      0.0000065/oF
Concrete     0.0000108/oC      0.000006/oF
--------------------------------------------
Unit Weights

                            Metric Value               English Value
--------------------------------------------------------------------------
Steel                       7848.3 kg/m3                  490 pcf
Concrete                    2402.5 kg/m3                  150 pcf
--------------------------------------------------------------------------

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The Construction Trades

THE CONSTRUCTION TRADES
            

Here are the metric units that will be used by the construction trades. The term "length" includes all linear measurements--length, width, height, thickness, diameter, and circumference.

                     Quantity                   Unit                           Symbol
Surveying            length                     kilometer, meter               km, m
                     area                       square kilometer               km2
                                                hectare (10,000 m2)            ha
                                                square meter                   m2
                     plane angle                degree (non metric)            o
                                                minute (non metric)            '
                                                second (non metric)            "

Excavating           length                     meter, millimeter              m, mm
                     volume                     cubic meter                    m3

Trucking             distance                   kilometer                      km
                     volume                     cubic meter                    m3
                     mass                       metric ton (1000 kg)           t

Paving               length                     meter, millimeter              m, mm
                     area                       square meter                   m2

Concrete             length                     meter, millimeter              m, mm
                     area                       square meter                   m2
                     volume                     cubic meter                    m3
                     temperature                degree Celsius                 oC
                     water capacity             liter (1000cm)                 L
                     mass (weight)              kilogram, gram                 kg, g
                     cross-sectional area       square millimeter              mm2
                        

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Pipe Conversion Factors

Pipe is one of the most ubiquitous products in construction. It is made of a wide variety of materials, including galvanized steel, black steel, copper, cast iron, concrete, and various plastics such as ABS, PVC, CPVC, polyethylene, and polybutylene, among others.

But like wood 2-by-4's which are not really 2 inches by 4 inches, pipe is identified by "nominal" or "trade" names that are related only loosely to actual dimensions. For instance, a 2-inch galvanized steel pipe has n inside diameter of about 2-1/8 inches and an outside diameter of about 2-5/8 inches. It is called "2-inch pipe" only for the sake of convenience.

Since few, if any, pipe products have actual dimensions that are in even, round inch-pound numbers, there is no need to convert them to even, round metric numbers. Instead, only their names will change--from inch-pound to metric. Pipe cross sections will not change. Fittings, flanges, couplings, valves, and other piping components will be renamed in like manner as will pipe threads. Here are the inch-pound names for pipe products (called NPS or "nominal pipe size") and their metric equivalents (called DN or "diameter nominal"). The metric names conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas, heating oil, drainage, and miscellaneous piping used in buildings and civil works projects.

            NPS          DN          NPS          DN 
            ----------------------------------------
            
            1/8"        6 mm         8"         200 mm
            3/16"       7 mm        10"         250 mm
            1/4"        8 mm        12"         300 mm
            3/8"       10 mm        14"         350 mm
            1/2"       15 mm        16"         400 mm
            5/8"       18 mm        18"         450 mm
            3/4"       20 mm        20"         500 mm
             1"        25 mm        24"         600 mm
           1-1/4"      32 mm        28"         700 mm
           1-1/2"      40 mm        30"         750 mm
             2"        50 mm        32"         800 mm
           2-1/2"      65 mm        36"         900 mm
             3"        80 mm        40"        1000 mm
           3-1/2"      90 mm        44"        1100 mm
             4"       100 mm        48"        1200 mm
           4-1/2"     115 mm        52"        1300 mm
             5"       125 mm        56"        1400 mm
             6"       150 mm        60"        1500 mm
  **(For pipe over 60 inches, use 1 inch equals 25 mm)

                        

TABLE 1	PROPOSED METRIC CSP DIAMETER SIZES
	Proposed Metric (mm)	Current Standard (inches)

               150                        6
               200                        8
               250                       10
               300                       12
               375                       15
               450                       18
               525                       21
               600                       24
               675                       27
               750                       30
               825                       33
               900                       36
               1050                      42
               1200                      48
               1350                      54
               1500                      60
               1650                      66
               1800                      72
               1950                      78
               2100                      84
               2250                      90
               2400                      96
               2550                      102
               2700                      108
               2850                      114
               3000                      120
               3150                      126
               3300                      132
               3450                      138
               3600                      144

            

TABLE 2

                          CORRUGATION SIZES
            
                  CURRENT                    PROPOSED 
                 (Inches)                 (Millimeters)
-------------------------------------------------------------------

               2 2/3 x 1/2                   68 x 13

                   3 x 1                     76 x 25

                   5 x 1                    125 x 25

              3/4 x 3/4 x 7 1/2           19 x 19 x 191

              3/4 x 1 x 11 1/2            19 x 25 x 292

            

            

            

                        

TABLE 3
                              PIPE WALL THICKNESS
         CURRENT                   NOMINAL                  PROPOSED
                                  Thickness                  NOMINAL
                                                            Thickness
    ---------------------------------------------------------------------

          GATE                   (Inches)                (millimeters) 
           16                      0.064                       1.6
           14                      0.079                       2.0
           12                      0.109                       2.8
           10                      0.138                       3.5
            8                      0.168                       4.3

            

TABLE 4

                                PIPE ARCH SIZES
            
            Corrugations                             Corrugations
     Inches       Millimeters              Inches           Millimeters
   2 2/3 x 1/2      68 x 13            3 x 1 & 5 x 1    76 x 25 & 125 x 25
   Span x Rise    Span x Rise            Span x Rise        Span x Rise
---------------------------------------------------------------------------------
    17 x 13        425 x 325               53 x 41          1325 x 1025
    21 x 15        525 x 375               60 x 46          1500 x 1150
    24 x 18        600 x 450               66 x 51          1650 x 1275
    28 x 20        700 x 500               73 x 55          1825 x 1375
    35 x 24        875 x 600               81 x 59          2025 x 1475
    42 x 29       1050 x 725               87 x 63          2175 x 1575
    49 x 33       1225 x 825               95 x 67          2375 x 1675
    57 x 38       1425 x 950              103 x 71          2575 x 1775
    64 x 43       1600 x 1075             112 x 75          2800 x 1875
    71 x 47       1775 x 1175             117 x 79          2925 x 1975
    77 x 52       1925 x 1300             128 x 83          3200 x 2075
    83 x 57       2075 x 1425             137 x 87          3425 x 2175
   142 x 91       3550 x 2275
Note: millimeters equal to inches x 25. Assumed pipe diameters will be x 25.

TABLE 4A			PIPE ARCH SIZES
                                 CORRUGATIONS
                Inches                                  Millimeters
           3/4 x 3/4 x 7 1/2                           19 x 19 x 191
              Span x Rise                               Span x Rise
----------------------------------------------------------------------------
                20 x 16                                  500 x 400
                23 x 19                                  575 x 475
                27 x 21                                  675 x 525
                33 x 26                                  825 x 650
                40 x 31                                 1000 x 775
                46 x 36                                 1150 x 900
                53 x 41                                 1325 x 1025
                60 x 46                                 1500 x 1150
                66 x 51                                 1650 x 1275
                73 x 55                                 1825 x 1375
                81 x 59                                 2025 x 1475
                87 x 63                                 2175 x 1575
                95 x 67                                 2375 x 1675
Note: millimeters equal to inches x 25. Assumed pipe diameters will be x 25.

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Structural Plate Conversion Factors

                         STRUCTURAL PLATE DIMENSIONS

                            6 X 2 Corrugation
                          31 Inch Corner Radius
         ------------------------------------------------------
           Span              Rise             R           R
          ft-in              ft-in           ft.         ft.
         ------------------------------------------------------
          13-3                9-4            6.68       16.05
          14-11              10-2            7.48       18.98
          16-6               11-0            8.29       21.93
          18-1               11-10           9.09       24.98
          19-8               12-8            9.90       28.04


TABLE 5M  STRUCTURAL PLATE DIMENSIONS

                            152 x 51 Corrugation
                            787 mm Corner Radius
       ___________________________________________________________ 
                                millimeters
       -----------------------------------------------------------
          Span               Rise               R             R 
       ___________________________________________________________
          4039               2845             2036          4892
          4547               3099             2280          5785
          5029               3353             2527          6684
          5512               3607             2771          7614
          5994               3861             3018          8547

                        

TABLE 6  			STRUCTURAL PLATE THICKNESS 

          Current   Specification                    Proposed
         ________________________________________________________
           Gage        Inches                       Millimeters
         ________________________________________________________
            12         .111                              2.5
            10         .140                              3.5
             8         .170                              4.5
             7         .188                               -
             5         .218                              5.5
             3         .249                              6.5
             1         .280                              7.0
            5/16       .318                              8.0
            3/8        .377                              9.5

            

 

 

 

 

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