FORJAY Machine Shop

The International System of Units (SI)

SI Base Units
Quantity Name Symbol
Length meter, metre m
Mass kilogram kg
Time second s
Electric Current ampere A
Temperature kelvin K
Amount of Substance mole mol

Some SI Derived Units
Quantity Name Formula Special
Symbol
Area square metre m2 -
Volume cubic metre m3 -
Velocity metre per second m/s -
Density kilogram per cubic metre kg/m3 -
Concentration moles per cubic metre mol/m3 -
Force newton kg-m/s2 N
Energy joule kg-m2/s2, N-m J
Stress pascal kg/m-s2, N/m2 Pa
Strain - m/m -
Power, radiant flux watt kg-m2/s3, J/s W
Viscosity pascal-second kg/m-s Pa-s
Frequency hertz s-1 Hz
Electric Charge coulomb A-s C
Electric potential volt kg-m2/s2-C V
Capacitance farad s2-C/kg-m2 F
Electric Resistance ohm kg-m2/s-C2 Ω
Magnetic flux weber kg-m2/s-C Wb
Magnetic flux density tesla kg/s-C, Wb/m2 T

Some SI Prefixes
Factor Prefix Symbol
1021 zetta Z
1018 exa E
1015 peta P
1012 tera T
109 giga G
106 mega M
103 kilo k
10-2 centi c
10-3 milli m
10-6 micro μ
10-9 nano n
10-12 pico p
10-15 femto f
10-18 atto a
10-21 zepto z

Some SI Unit Conversion Factors
Quantity Conversion Factors
Length 1 mm = 0.03937008 inch
1 m = 3.280839895 ft
1 m = 1.093613298 yard
1 inch = 25.4 mm
1 ft = 0.3048 m
1 yard = 0.9144 m
Area 1 m2 = 10.76391042 ft 2
1 ft2 = 0.09290304 m2
Volume 1 m3 = 35.31466672 ft3
1 ft3 = 0.028316847 m3
Mass 1 kg = 2.20462262 lb
1 lb = 0.45359237 kg
Density 1 kg/m3 = 10-3 g/cm3
1 lb/ft3 = 16.02 kg/m3
Force 1 N = 0.2248 lb
1 lb = 4.448 N
Stress 1 MPa = 145 psi
1 psi = 0.0069 MPa
Energy 1 J = 0.239 cal
1 J = 0.000948 Btu
Temperature T(K) = 273 + T(°C)
T(K) = (5/9)[T(°F) - 32] + 273
T(°C) = (5/9)[T(°F) - 32]