## Useful Tables

#### Table 1a. SI Base Units

SI Unit Quantity Name length meter m mass1 kilogram kg time second s electric current ampere A thermodynamic temperature kelvin K amount of substance mole mol luminous intensity candela cd

1 "Weight" in common parlance is often used to mean "mass."

#### Table 2. Examples of SI Derived Units Expressed in Terms of Base Units

SI Unit Quantity Name area square meter m2 volume cubic meter m3 speed, velocity meter per second m/s acceleration meter per second squared m/s2 wave number reciprocal meter m-1 density, mass density kilogram per cubic meter kg/m3 specific volume cubic meter per kilogram m3/kg current density ampere per square meter A/m2 magnetic field strength ampere per meter A/m concentration (of amount of substance) mole per cubic meter mol/m3 luminance candela per square meter cd/m2

#### Table 3. SI Derived Units with Special Names

SI Unit Quantity Name Symbol frequency hertz Hz s-1 force newton N m·kg/s2 pressure, stress pascal Pa N/m2 energy, work, quantity of heat joule J N·m power, radiant flux watt W J/s electric charge, quantity of electricity coulomb C s·A electric potential, poetential difference, electromotive force volt V W/A capacitance farad F c/V electric resistance ohm V/A electric conductance siemens S A/V magnetic flux weber Wb V·s magentic flux density tesla T Wb/m2 inductance henry H Wb/A Celsius temperature1 degree Celsius °C K luminous flux lumen lm cd·sr illuminance lux lx lm/m2 activity (of a radionuclide) becquerel Bq s-1 absorbed dose, specific energy imparted, kerma, absorbed dose index gray Gy J/kg dose equivalent, dose equivalent index sievert Sv J/kg

1 In addition to the thermodynamic temperature (symbol T) expressed in kelvins (see Table 1a), use is also made of Celsius temperature (symbol t) defined by the equation t=T-T0 where T0=273.15 K by definition. To express Celsius temperature, the unit "degree Celsius" which is equal to the unit "kelvin" is used; in this case, "degree Celsius" is a special name used in place of "kelvin." An interval or difference of Celsius temperatures can, however, be expressed in kelvins as well as in degrees Celsius.

#### Table 4. Examples of SI Derived Units Expressed by Means of Special Names

SI Unit Quantity Name dynamic viscosity pascal second PA·s moment of force newton meter N·m surface tension newton per meter N/m heat flux density, irradiance watt per square meter W/m2 heat capacity, entropy joule per kelvin J/K specific heat capacity, specific entropy joule per kilogram kelvin J(kg·K) specific energy joule per kilogram J/kg thermal conductivity watt per meter kelvin W/(m·K) energy density joule per cubic meter J/M3 electric field strength volt per meter V/m electric charge density coulomb per cubic meter C/m3 electric flux density coulomb per square meter C/m2 permittivity farad per meter F/m permeability henry per meter H/m molar energy joule per mole J/mol molar entropy, molar heat capacity joule per mole kelvin J/(mol·K) exposure (x and ) coulomb per kilogram C/kg absorbed dose rate gray per second Gy/s

#### Table 6. SI Prefixes

Factor Prefix Symbol
1024 yotta Y
1021 zetta Z
1018 exa E
1015 peta P
1012 tera T
109 giga G
106 mega M
103 kilo k
102 hecto h
101 deka da
10-1 deci d
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
10-24 yocto y

#### Table 7. Units in Use with the International System

Name Symbol Value in SI unit
minute (time) min 1 min=60 s
hour h 1 h=60 min=3 600 s
day d 1 d=24 h=86 400 s
minute (angle) ' 1'=(1/60)°=(/10 800) rad
second (angle) " 1"=(1/60)'=(/648 000) rad
1liter L 1 L=1 dm3=10-3 m3
2metric ton t 1 t=103 kg
hectare (land area) ha 1 ha=1 hm2=104 m2
3electronvolt eV 1eV=1.602 18×10-19 J, approximately
3unified atomic mass unit u 1 u=1.660 54×10-27 kg, approximately

1 Both L and l are internationally accepted symbols for liter. Because "l" can easily be confused with the numeral "1," the symbol "L" is recommended for United States use.

2 In many countries, this unit is called "tonne."

3 The values of these units expressed in terms of SI units must be obtained by experiment, and are therefore not known exactly. The electronvolt is the kinetic energy acquired by an electron passing through a potential difference of 1 volt in vacuum. The unified atomic mass unit is equal to (1/12) of the mass of the atom of the nuclide 12C.

#### Table 8. Units in Use Temporarily with the International System

 nautical mile barn roentgen knot bar rad3 ångström gal2 rem4 are1 curie

1 Unit of land area.

2 Unit of acceleration.

3 Unit of absorbed dose.

4 Unit of dose equivalent.

--Physics Laboratory, National Institute of Standards and Technology

## Useful Tables ##