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 case-sensitive. | 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
kilowatt-hour |
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 | 1015 | 1.2 Pm |
| tera | T | 1012 | 2.3 terajoule |
| giga | G | 109 | 3.4 Gg |
| mega | M | 106 | 4.5 megavolt |
| kilo | k | 103 | 5.6 km |
| hecto | h | 102 | 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 |