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Common Units of Measure

This list contains frequently encountered units but excludes SI base units.

A ampere (electric current)
Å angstrom (101 nm distance; do not define unless specifically indicated)
A·h ampere hour
AM ante meridiem
A·s ampere second
ATA  atmosphere absolute
atm  atmosphere
B bel
Bq becquerel (radioactivity)
bar  (no abbreviation) (105 Pa)
beats/min beats per minute (heart rate; do not use bpm)
BeV billion electron volts
bp base pair
C coulomb (electric charge)
°C degree Celsius
cal  calorie
cd candela (luminance)
Ci curie
clo reciprocal of thermal conductance
cmH2O centimeter of water
counts/s counts per second
cP centipoise (viscosity)
cpm counts per minute (define as counts/min)
cw continuous wave
cycles/deg cycles/degree (unit symbol is "°/s"; e.g., 15°/s)
cycles/min  cycle per minute
cycles/s cycles/second (Hz)
D debye; darcy
Da dalton (molecular mass)
dB decibel
deg or ° degree (see above)
dpm disintegrations per minute (define as disintegrations/min)
dyn dyne
eq equivalents
eV electron volts
F farad (electric capacitance)
ft foot
ft.-cd foot candle
ft.-L foot lambert
G gauss
G gravitational constant
g gravity (e.g., 1,000 g)
g·atom gram·atom
g·cm  gram·centimeter
g·min  product of acceleration & time specifying speed & duration of centrifugation
g·mol gram·molecule
gr grain
Gy gray (absorbed dose)
H henry (electric inductance)
H1 reciprocal henry
hp horsepower
Hz hertz (cycles/s; frequency)
imp impulse
in. inch
in./s inch per second
IU international unit
J joule (energy, work, quantity of heat)
K Kelvin (use °K if there is risk of confusion with other variables)
kb kilobase
kcal kilocalorie (change Cal to kcal)
kgH2O kilogram H2O (always bumped)
kg·m kilogram·meter (work)
kpm  kilopond·meter (work)
L lambert (watch out for " L" used incorrectly as "liter")
l liter (volume; spell out when used alone)
lb. pound
lb./in.2 pound per inch squared (do not use psi)
lm  lumen (luminous flux)
lx lux (illuminance)
M molar (mM = millimolar = mmol/l)
mho  reciprocal Ω (change to S for siemens) (1/Ω)
m·L meter lambert
mmHg millimeters of mercury (always bumped)
mol/kg  mole per kilogram (molal)
mol/l  mole per liter
mph  mile per hour
MW·h  megawatt hour
N normal
N Newton (force)
N/s Newtons per second (rate of force development)
N·s Newtons times seconds (force)
N/m2  newton per meter squared
N·m/deg newton meter per degree
np nepers (log of intensity ratio)
Ω ohm (electric resistance)
osM osmolar (osmolarity)
osmol/kgH2O osmolal (osmolality; sometimes authors use mOsm — change to mosmol/kgH2O and query author)
oz  ounce
P Poise
Pa pascal (pressure, stress)
pack·yr pack/day × years of smoking
PM post meridiem (sm caps)
ppm part per million
% percent (no space; e.g., 10%)
R roentgen
rad  absorbed dose of ionizing radiation
rad radian (plane angle)
rpm revolutions per minute (define as revolution/min)
rps revolutions per second
S Siemens (mho) (conductance)
spikes/s spikes/second (don't abbrev. spikes)
slyke millimole per pH unit
sr steradian (solid angle)
Sv sievert (dose equivalent)
t metric ton (mass)
T tesla
Torr torr (equals 1 mmHg; in JAP, always use Torr, not mmHg, to express blood gas values such as PO2, PCO2, etc.)
U units
u atomic mass unit
V volts (electrical potential, potential difference)
W watt (power, radiant flux)
Wb weber (magnetic flux)
W·h watt·hour
z atomic number

Units of Time

day  not abbreviated
hour 
min  minute 
mo  month 
s second 
wk  week 
yr  year* 

*When years is used in a historical context, do not abbreviate.

When an author uses "military time" (24-h clock; prevalent in Europe), do not change to 12-hour time. Delete the colon between the hours and minutes if one is used, and delete the abbreviation "h" for hours if it is present.

At 1800 we fed the animals with...

At 6 PM, the animals received an injection of...

The rats were exposed to light daily, between 0630 and 1830 (12-h light-dark cycle).

Methods of Drug Delivery

The following terms are spelled out when part of a sentence; however, they must be abbreviated when used after a number and/or a unit of measure, usually in the form of a dosage (e.g., "16 mg/kg iv").

body wt  body weight
ia intra-arterial
ic intracutaneous
icv intracerebroventricular
id intradermal
im intramuscular
ip intraperitoneal
iv intravenous
po per os (oral)
sc subcutaneous

Methods of drug delivery may be abbreviated in text if they appear frequently. In such a case, they must be defined at first occurence. They do not require definition when used with numerical values and units. Note lack of periods after these abbreviations. 

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last edited 07/29/03