CONVERSION FACTORS Part 1 (Molecular Biology)
SI Units (Adopted 1960)
The International System of Units (abbreviated SI), is being implemented throughout the world. This measurement system is a modernized version of the MKSA (meter, kilogram, second, ampere) system, and its details are published and controlled by an international treaty organization (The International Bureau of Weights and Measures) (1). SI units are divide^ into three classes:
BASE UNITS
length


mass "

kilogram (kg)

time

second (s)

electric current

ampere (A)

thermodynamic temperature*

kelvin (K)

amount of substance

mole (mol)

luminous intensity

candela (cd)

SUPPLEMENTARY UNITS
plane angle

radian (rad)

solid angle

steradian (sr)

DERIVED UNITS AND OTHER ACCEPTABLE UNITS
These units are formed by combining base units, supplementary units, and other derived units (24). Those derived units having special names and symbols are marked with an asterisk in the list below.
Quantity

Unit

Symbol

Acceptable equivalent

absorbed dose

gray


J/kg

acceleration

meter per second squared



activity (of a radionuclide)

becquerel


1/8

area

square kilometer




square hectometer


ha (hectare)


square meter



concentration (of amount of substance)

mole per cubic meter



current density

ampere per square meter



density, mass density

kilogram per cubic meter



dipole moment (quantity)

coulomb meter



Quantity

Unit

Symbol

Acceptable equivalent

dose equivalent

sievert



electric capacitance

farad



electric charge, quantity of electricity

coulomb



electric charge density

coulomb per cubic meter



♦electric conductance

siemens



electric field strength

volt per meter



electric flux density

coulomb per square meter



♦electric potential, potential difference,

volt



electromotive force




♦electric resistance

ohm



♦energy, work, quantity of heat

megajoule




kilojoule




joule




electronvolt^{1}




kilowatthour*



energy density

joule per cubic meter



♦force

kilonewton




newton



♦frequency

megahertz




hertz



heat capacity, entropy

joule per kelvin



heat capacity (specific), specific entropy

joule per kilogram kelvin



heattransfer coefficient "

watt per square meter kelvin



♦illuminance

lux



♦inductance

henry



linear density

kilogram per meter



luminance

candela per square meter



♦luminous flux

lumen



magnetic field strength

ampere per meter



♦magnetic flux

weber



♦magnetic flux density

tesla



molar energy

joule per mole



molar entropy, molar heat capacity

joule per mole kelvin



moment of force, torque

newton meter



momentum

kilogram meter per second



permeability

henry per meter



permittivity

farad per meter



♦power, heat flow rate, radiant flux

kilowatt




watt



power density, heat flux density,

watt per square meter



irradiance




♦pressure, stress

megapascal




kilopascal




pascal



sound level

decibel



specific energy

joule per kilogram



specific volume

cubic meter per kilogram



surface tension

newton per meter



thermal conductivity

watt per meter kelvin



velocity

meter per second




kilometer per hour



viscosity, dynamic

pascal second




millipascal second



viscosity, kinematic

square meter per second




square millimeter per second



volume

cubic meter




cubic diameter




cubic centimeter



wave number

1 per meter




1 per centimeter



^{t}This nonSI unit is recognized by the CIPM as having to be retained because of practical importance or use in specialized fields (1).
In addition, there are 16 prefixes used to indicate order of magnitude, as follows:
Multiplication factor

Prefix

Symbol

Note


exa

E



peta

P



tera

T



giga

G



mega

M



kilo

k



hecto


"Although hecto, deka, deci, and centi are SI prefixes, their use


deka


should be avoided except for SI unitmultiples for area and


deci


volume and nontechnical use of centimeter, as for body and


centi

c^{a}

clothing measurement.


milli

m



micro




nano

n



pico

P



femto

f



atto

a


For a complete description of SI and its use the reader is referred to ASTM E380 (4).
A representative list of conversion factors from nonSI to SI units is presented herewith. Factors are given to four significant figures. Exact relationships are followed by a dagger. A more complete list is given in the latest editions of ASTM E380 (4) and ANSI Z210.1 (6).