This page discusses how units are represented as strings. There is also a table of standard prefixes, and a table of built in units. This information applies to both the Java Library and the PalmOS application.
You may use
a combination of any of the standard units, including standard prefixes.
Strings are case sensitive
mm is millimeter, Mm is megameter, and MM
will generate an error.
Each unit is made up of a fraction of other units. Everything to the left of
the slash is in the numerator and everything to the right is in the denominator
-- parenthesis are not used (it's a feature...).
Multiplication is just denoted by whitespace, and the exponent symbol is a
caret: "^". Exponents may be positive or negative, but they must be
integers.
For example the unit
kW/m^2 is the same as 1715 times the unit BTU/h ft^2.
The common temperature units, Centigrade or Celsius (°C) and Fahrenheit (°F), have an offset when compared to the default Kelvin (K). For this software, changes in temperature should use an absolute scale, such as Kelvin (K) or Rankine (R). In this software, 20 C - 10 C = 10 K. But 10 K = -263 C. So in this software, if we just subtract 20 C - 10 C, we would get -263 C. The bottom line is that we should not use Celsius or Fahrenheit when adding or subtracting, and probably not when multiplying or dividing.
Any unit may be preceded by a prefix to denote a multiplier. For example, one "dain" would be 10 inches.
| Prefix used in code | Prefix for written unit | Multiplier |
|---|---|---|
| da- | deka- or deca- | 10 |
| h- | hecto- | 100 |
| k- | kilo- | 1000 |
| M- | mega- | 1e6 |
| G- | giga- | 1e9 |
| T- | tera- | 1e12 |
| P- | peta- | 1e15 |
| E- | exa- | 1e18 |
| Z- | zeta- | 1e21 |
| Y- | yotta- | 1e24 |
| d- | deci- | 1e-1 |
| c- | centi- | 1e-2 |
| m- | milli- | 1e-3 |
| mu- | micro- | 1e-6 |
| n- | nano- | 1e-9 |
| p- | pico- | 1e-12 |
| f- | femto- | 1e-15 |
| a- | atto- | 1e-18 |
| z- | zepto- | 1e-21 |
| y- | yocto- | 1e-24 |
| Unit | Symbol | Definition | Comments |
|---|---|---|---|
| Time | |||
| second | sec | 1 s | |
| minute | min | 60 s | |
| hour | hr | 60 min | |
| hour | hour | 1 hr | alternate symbol |
| hour | h | 1 hr | alternate symbol |
| day | day | 24 hr | |
| shake | shake | 10 ns | |
| Hertz | Hz | 1 s^-1 | |
| week | week | 7 day | |
| fortnight | fortnight | 14 day | |
| work week | week_wk | 40 hour | |
| month | month | 30 day | This is just for rough estimates, but I find it useful. |
| standard year | year_std | 365 day | This is not to be used in astronomical computations. |
| Length or Distance | |||
| international foot | ft | 0.3048 m | |
| inch | in | 1.0/12.0 ft | |
| international mile | mile | 5280.0 ft | |
| international mile | mi | 1 mile | alternate symbol |
| nautical mile | nmi | 1852 m | |
| milli-inch | mil | 0.001 in | |
| micron | micron | 1e-6 m | |
| Parsec | pc | 3.085678e16 m | |
| League | league | 3 mile | |
| Astronomical Unit | ua | 1.49598e11 m | |
| Astronomical Unit | AU | 1.49598e11 m | alternate symbol |
| yard | yd | 3 ft | |
| Angstrom | Ang | 1e-10 m | (I call it Ang, because I can't spell Å in java) |
| Angstrom | \\AA | 1 Ang | alternate symbol |
| furlong | furlong | 220 yd | |
| fathom | fathom | 6 ft | (my dad is sea foam) |
| Rod | rd | 16.5 ft | |
| U.S. survey foot | sft | (1200./3937.) m | |
| U.S. survey mile | smi | 5280 sft | also called statue mile |
| cubit | cubit | 18 in | rough approximation |
| point | pt | 1./72. in | Typeface Point |
| pica | pica | 1./6. in | Typeface Pica |
| Temperature | |||
| Celsius | C | 1 K -273.15 | |
| Rankine | R | 5.0/9.0 K | |
| Fahrenheit | F | 1 R -459.67 | |
| Mass | |||
| gram | g | 0.001 kg | This is case sensitive. |
| gram | gm | g | (alternate symbol) |
| pound mass | lbm | 0.45359237 kg | (avoirdupois) |
| slug | slug | 1 lb sec^2/ft | |
| snail | snail | 1 lb sec^2/in | |
| Ounce | oz | 1.0/16.0 lbm | (avoirdupois) |
| dram | dram | 1.0/16.0 oz | (avoirdupois) Dram is short for drachm |
| Short Ton | ton | 2000 lbm | |
| Long Ton | ton_l | 2240 lbm | |
| Pennyweight | dwt | 24 gr | (troy) |
| Troy ounce | ozt | 480 gr | (apothecary) |
| Troy pound | lbt | 5760 gr | (apothecary) |
| carat (metric) | carat | 0.2 g | |
| Grain | gr | 1.0/7000.0 lbm | |
| Stone | stone | 14 lbm | |
| Hundredweight | cwt | 8 stone | |
| Force or Weight | |||
| Newton | N | 1 kg m/s^2 | |
| Dyne | dyn | 1e-5 N | |
| pound force | lb | lbm G | |
| pound force | lbf | lbm G | |
| poundal | poundal | 1 lbm ft/sec^2 | |
| kilopound | kip | 1000 lbf | |
| kilogram force | kgf | kg G | |
| Energy | |||
| Joule | J | 1 N m | |
| British Therm. Unit | BTU | 1055.056 J | (International Table) |
| British Therm. Unit | Btu | 1 BTU | alternate symbol |
| British Therm. Unit | BTU_th | 1054.350 J | (Thermochemical) |
| calorie | cal | 4.1868 J | (International Table) |
| calorie | cal_th | 4.184 J | (Thermochemical) |
| Calorie | Cal | 1 kcal | (nutritionists) |
| electron volt | eV | 1.602177e-19 J | |
| erg | erg | 1e-7 J | |
| Ton of TNT | TNT | 4.184e9 J | |
| Power | |||
| Watt | W | 1 J/s | |
| Horse Power | hp | 550 ft lb/s | |
| Pressure | |||
| bar | bar | 1e5 N/m^2 | |
| Pascal | Pa | 1 N/m^2 | |
| Pounds per sq. inch | psi | 1 lb/in^2 | |
| Pounds per sq. ft. | psf | 1 lb/ft^2 | |
| kilo psi | ksi | 1000.0 psi | |
| atmospheres | atm | 1.01325e5 N/m^2 | |
| millimeters Mercury | mmHg | 1.0/760.0 atm | Pressure needed to raise a column of mercury 1 mm. |
| inches of Mercury | inHg | 1 mmHg in/mm | |
| Torr | torr | 1 mmHg | Used in the Torricelli barometer |
| Volume or Area | |||
| Liter | L | 1/1000.0 m^3 | |
| Pint (U.S. dry) | dpint | 0.5506105 L | |
| Quart (U.S. dry) | dqt | 2 dpint | |
| Acre | acre | 1/640.0 mi^2 | |
| Hectare | ha | 10000 m^2 | |
| Barrel (petroleum) | barrel | 158.9873 L | |
| Peck (U.S.) | pk | 8.809768 L | |
| Teaspoon | tsp | 1/768. gal | |
| Tablespoon | tbl | 3 tsp | |
| Fluid Ounce | oz_fl | 2 tbl | |
| Gill (U.S.) | gi | 8 tbl | |
| Cup | cup | 16 tbl | |
| Pint (U.S. liquid) | pint | 2 cup | |
| Quart (U.S. liquid) | qt | 2 pint | |
| gallon | gal | 3.785412 L | |
| firkin | firkin | 9 gal | |
| hogshead | hogshead | 63 gal | |
| Electromagnetism | |||
| Coulomb | Co | 1 A s | Electric Charge |
| Volt | V | 1 W/A | Electric Potential |
| Ohm | ohm | 1 V/A | Electric Resistance |
| Ohm | \\Omega | 1 V/A | alternate symbol |
| Faraday | faraday | 96485.31 Co | Electric Charge |
| Farad | farad | Co/V | Capacitance |
| Stokes | stokes | 1e-4 m^2/s | |
| Oersted | Oe | 79.57747 A/m | |
| Webber | Wb | V s | Magnetic flux |
| Tesla | Tesla | Wb/m^2 | Magnetic flux density |
| Henry | H | Wb/A | Inductance |
| Siemens | S | A/V | Electrical Conductance |
| Light and Radiation | |||
| Lux | lux | cd/m^2 | Iluminance |
| Lux | lx | cd/m^2 | |
| Lumen | lm | cd | Luminous Flux |
| Stilb | sb | 10000 cd/m^2 | |
| Phot | ph | 10000 lx | |
| Becquerel | Bq | s^-1 | activity |
| Gray | Gy | J/kg | Absorbed Dose, kerma |
| Sievert | Sv | J/kg | Dose equivalent |
| Other Quantities | |||
| pound mole | lbmole | 1 mol lbm/g | quantity |
| gram mole | gmole | 1 mol g/g | quantity |
| poise | poise | 1 g /sec cm | viscocity |
| Gravity's accel. | G | 9.80665 m/sec^2 | Gravity on Earth |
| Galileo | Gal | 1 cm/sec^2 | Used in Geology, when measuring gravity. |
| Degree | deg | Pi/180 | Can be used to convert from degrees to radians for trig functions. |
| radian | rad | 1 | Actually, radian is a pure number. |
| steradian | st | 1 | The unit surface area of a unit sphere. It is really a pure number. |
| Percent | % | 0.01 | |
| Knot | knot | 1 nmi/hr | velocity |
| Miles per Hour | mph | 1 mi/hr | velocity |
| Gallon/minute | gpm | 1. gal/min | flow rate |
| Revolution/minute | rpm | 360 deg/min | |
| Obscure | |||
| ch'ih | chih | 10.0/33.0 m | Chinese |
| feddan | feddan | 1.038 acre | Egyptian |
| vara | vera | 0.84 m | Nicaraguan |
| verst | verst | 1.067 km | Russan |
| Humor | |||
| 1 million microphones | 1 megaphone | (it's a joke! Get it?) | |
| 1 million bicycles | 2 megacycles | ||
| 2000 mockingbirds | 2 kilomockingbirds | ||
| 10 cards | 1 decacards | (or is it 52 cards = 1 deck-a-cards?) | |
| 1/2 lavatory | 1 demijohn | ||
| 1 millionth of a fish | 1 microfiche | ||
| 453.6 graham crackers | 1 pound cake | ||
| 10 rations | 1 decoration | ||
| 1 ship | 1 millihelen | ||
| 10 millipedes | 1 centipede | ||
| 3-1/3 tridents | 1 decadent | ||
| 10 monologs | 5 dialogues | ||
| 2 monograms | 1 diagram | ||
| 8 nickles | 2 paradigms | ||
Notice that lb is pound force. If you wish to use pound mass, you should use lbm.
Most of the conversion factors are taken from the U.S. National Institute of Standards and Technology, NIST. According to NIST, the BTU and calorie were redefined at the Fifth International Conference on the Properties of Steam (London, July 1956). These are marked as International Table above. An alternate definition is listed as "Thermochemical".
Internally, a unit is represented in terms of the primitive units:
m (meters),
s (seconds),
kg (kilograms),
K (Kelvin),
mol (Moles),
A (Amperes),
and
cd (candelas).
Any unit can be represented as a product of powers of these primitive units.
These units form the basis for the International Standard (SI) system.