Many different unit names and abbreviations can be used in numerical questions requiring units.
Rules for Units
Observe the following rules when specifying units.
Rule  Incorrect  Correct 

Type a space between the number and the unit.  20g
20 g 
20 g 
Units are casesensitive.  1 minute = 60 S  1 minute = 60 s 
Do not combine multiple values and units.  3 minutes 15 seconds  3.25 minutes 
To change the dimension of a unit, follow the unit with a caret
(^) and an exponent. Do not use the words squareor cubic.Do not use two asterisks (**) to specify the exponent. 
3 square miles
3 mi**2 
3 mi^2 
To divide a unit, use /. Do not use per. 
miles per hour  miles/hour 
To multiply a unit, use a space or asterisk. Do not use a raised dot or hyphen.  kW·h
kilowatthour 
kW*h
kilowatt hour 
Many unit names accept singular and plural forms interchangeably. Do not pluralize unit abbreviations.  3 mis  3 mi
3 miles 
Do not enter a fraction for the number when units are required.  3/4 inch  0.75 inch 
Units
This is not an exhaustive list, but includes the most commonly used units and abbreviations. For SI units, most derived units are not listed here.
Note For units having different values in different countries, the U.S. value is
used.
Unit  Abbreviation  Notes 

ampere  A  
angstrom  Å, ångström  
astronomicalunit  au, AU  
atmosphere  atm  
atomicmassunit  u, amu  
bar  
becquerel  Bq  
britishthermalunit  btu  
bushel  bu  
calorie  cal  
candela  cd  
candle  
carat  ct  
cc  Cubic centimeter. Do not use cubic centimeter.  
century  
click  
cm^3  Cubic centimeter. Do not use cubic centimeter.  
coulomb  C  
cup  
curie  Ci  
day  d  
decade  
diopter  The alternative spelling dioptrecan also be used. 

dollar  $  The unit must follow the number, as in 3.25 $. Do not specify $3.25. 
farad  F  
feet/minute  fpm  
feet/second  fps  
foot  ft  Alternatively, feet. 
foot^3/second  cfs  
gallon/hour  gal/h, gph  
gallon/minute  gpm  
gallon  gal  
grain  gr  
gram  g, gm  
henry  H  
hertz  Hz, hz  
horsepower  hp  
hour  h, hr  
inch  in  
joule  J  
kilocalorie  Calorie  
kilogram  kg  
kilometer/hour  kph  
kilowatt hour  kWh  
knot  
liter/minute  lpm  
liter/hour  L/h  
liter  L  The alternative spelling litrecan also be used. 
lumen  
mach  
meter  m  The alternative spelling metrecan also be used. 
mho  
micron  
microsecond  µs, us  
mile/gallon  mpg  
mile/hour  mph  
mile  mi  
minute  min  Use for time only. 
mmHg  
molar  M  
mole  mol  
nauticalmile  
newton  N  
ohm  You cannot use the Ω character.  
ounce  oz  
partsperbillion  ppb  Uses U.S. definition: 10^{9}. 
partspermillion  ppm  Uses U.S. definition: 10^{6}. 
partspertrillion  ppt  Uses U.S. definition: 10^{12}. 
pascal  Pa, pa  
picometer  pm  
pint  pt  
pound  lb  
proof  
psi  
quart  qt  
roentgen  rontgen, röntgen  
second  s, sec  Use for time only. 
sievert  Sv  
slug  
slugf  
solaryear  
tablespoon  tbl, tbsp  
teaspoon  tsp  
tesla  T  
torr  
volt  V  
watt  W  
weber  Wb  
week  wk  
yard  yd  
year  yr 
Combining Prefixes for SI Units
The following prefixes can be combined with SI base units to specify derived units. The derived unit or abbreviation cannot contain a space between the prefix and base unit.
Prefix  Abbreviation  Value  Example 

peta  P  10^{15}  1.2 Pm 
tera  T  10^{12}  2.3 terajoule 
giga  G  10^{9}  3.4 Gg 
mega  M  10^{6}  4.5 megavolt 
kilo  k  10^{3}  5.6 km 
hecto  h  10^{2}  6.7 hectometer 
deca, deka  da  10  7.8 dag 
deci  d  10^{1}  8.9 deciliter 
centi  c  10^{2}  9.0 cm 
milli  m  10^{3}  0.1 milliampere 
micro  µ
Note You cannot substitute u or
mu.

10^{6}  2.4 µg 
nano  n  10^{9}  4.6 nanosecond 
pico  p  10^{12}  6.8 ps 
femto  f  10^{15}  8.0 femtometer 