Unit Conversion Factors

ENGLISH UNITS

The following English units are commonly used in geotechnical engineering.

TABLE 1 Common English Units

Unit Measurement Symbol

Foot Distance ftInch Distance in.Pound Force or mass lbKip (kilopound) Force kipTon Force or mass tSecond Time sPound per square foot Stress or pressure or psflb/ft2

Pound per square inch Stress or pressure or psilb/in.2

Pound per cubic foot Unit weight or pcflb/ft3

SI AND METRIC UNITS

The following SI (Système International) units are commonly used in geotechnicalengineering.

TABLE 2 Common SI Units

Unit Measurement Symbol

Meter Distance MGram Mass gNewton Force NPascal Stress or pressure PaKilonewton per cubic meter Unit weight kN/m3

Second Time s

TABLE 3 Common SI Prefixes

Prefix Symbol Multiplier

milli m 10-3

centi c 10-2

kilo k 103

mega M 106

These units are often accompanied by the following prefixes.

Some non-SI metric units also are used, especially in Europe.The most common exampleis the use of as a unit of stress.kg/cm2

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TABLE 4 Units of Distance

To Convert To Multiply by

ft in. 12ft m 0.3048in. t 1/12in. mm 25.40m ft 3.281

mm in. 0.03937

CONVERSION FACTORS

The conversion factors in Tables 4–8 are useful for converting measurements betweenEnglish, metric, and SI units. Most of these factors are rounded to four significant figures.Those in bold type are absolute conversion factors (e.g., ). When units offorce are equated to units of mass, the acceleration is presumed to be

which is the acceleration due to gravity on the earth’s surface.There are at least three definitions for the word “ton”: the 2000-lb short ton

(commonly used in the United States and Canada), the 2240-lb long ton (used in GreatBritain), and the 2205-lb (1000 kg) metric ton (also known as a tonne).

A useful approximate conversion factor:atmosphere. These are true to within 2 to 4%.

1 short ton/ft2L 1kg/cm2

L 100 kPa L 1

9.807 m/s2 132.17 ft/s22,1F = ma2

12 in. = 1 ft

TABLE 5 Units of Force

To Convert To Multiply by

k kN 4.448k lb 1000

kgf lb 2.205kgf N 9.807kgf ton (metric) 0.001kN k 0.2248lb k 0.001lb kgf 0.4536lb N 4.448lb ton (short) 1/2000lb ton (long) 1/2240N kgf 0.1020N lb 0.2248

ton (short) lb 2000ton (long) lb 2240

ton (metric) kgf 1000

TABLE 6 Units of Volume

To Convert To Multiply by

ft3 gal 7.481gal ft3 0.1337

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TABLE 7 Units of Stress and Pressure

To Convert To Multiply by

atmosphere lb/ft2 2117atmosphere kPa 101.3

bar kPa 100kgf/cm2 kPa 98.07kgf/cm2 lb/ft2 2048

kPa atmosphere 0.009869kPa bar 0.01kPa kgf/cm2 0.01020kPa lb/ft2 20.89kPa lb/in.2 0.1450kPa metric ton/m2 0.1020lb/ft2 atmosphere 4.725 * 10-4

lb/ft2 kPa 0.04787lb/ft2 lb/in.2 1/144lb/in.2 kPa 6.895lb/in.2 lb/ft2 144lb/in.2 MPa 6.895 * 10-3

metric ton/m2 kPa 9.807MPa lb/in.2 145.0

TABLE 8 Units of Unit Weight

To Convert To Multiply by

kN/m3 lb/ft3 6.366kN/m3 metric ton/m3 0.1020kN/m3 Mgf/m

3 0.1020lb/ft3 kN/m3 0.1571

metric ton/m3 kN/m3 9.807Mgf/m

3 kN/m3 9.807

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