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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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