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Common Units & Unit Prefixes

The following tables list all of the available unit prefixes, and many of the most commonly used units in simulations at the NASA, Johnson Space Center - Engineering Branch.

Tables of units are provided for measuring time, length, angle, mass, force, volt, current, resistance, temperature, energy, power, pressure, volume, and frequency. Each of the rows in each of the tables contain a list of identifiers that refer to a particular unit. Each of the identifiers in a list is synonymous. Also, characters between brackets are optional. For example, "s", "second", "seconds" are treated as being identical.

It is important to note that these tables are not complete lists of all available units.

If you're really curious, or if you just can't find the units you need, you could run udunits2 -h on the command line, follow the default database path listed at the bottom of the help text, and examine the (fairly easy to read) UDUNITS2 xml database files. You could also use udunits2 with the -H option to determine whether the units you need exist, by guessing.

Unit Prefixes

Prefix Value
Y, yotta 1e24
Z, zetta 1e21
E, exa 1e18
P, peta 1e15
T, tera 1e12
G, giga 1e9
M, mega 1e6
k, kilo 1e3
h, hecto 100
da, deka 10
d, deci 0.1
c, centi 0.01
m, milli 1e-3
μ, u, 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

###Common Predefined Units

Time

Unit Identifier
s, second[s]
ms, millisecond[s]
μs, microsecond[s]
min, minute[s]
h, hour[s]
d, day[s]

Length

Unit Identifier
m, meter[s]
au, astronomical_unit[s]
nmile, nautical_mile[s]
ft, foot, feet
in, inch[es]
yd, yard[s]
mi, mile[s]
km, kilometer[s]
cm, centimeter[s]
mm, millimeter[s]
um, μm, micrometer[s]

Angle

Unit Identifier
rad, radian[s]
°, degree[s]
′, arcminute[s]
″, arcsecond[s]

Mass

Unit Identifier
kg, kilogram[s]
g, gram[s]
lb, pound[s]
slug, slug[s]

NOTE: For Trick 13 and earlier, use 'sl' instead of 'slug'.

Force

Unit Identifier
N, newton[s], kg.m/s^2, kg.m/s²
lbf, pound[s]_force

Voltage

Unit Identifier
V, volt[s]
mV, millivolt[s]
uV, μV, microvolt[s]

Current

Unit Identifier
A, amp, ampere
mA, milliamp
uA, μA, microamp

Resistance

Unit Identifier
Ω, ohm[s]
kΩ, kohm[s], kiloohm[s]
MΩ, Mohm[s], megaohm[s]

Temperature

Unit Identifier
K, °K, degK
°C, degC
°F, degF
°R, degR

Energy

Unit Identifier
J, joule[s]
MJ, Mjoule[s], megajoule[s]
W.h, watt.hour[s]
kW.h, kilowatt.hour[s]
BTU[s]

Power

Unit Identifier
W, watt
kW, kilowatt
MW, megawatt
hp, horsepower

Pressure

Unit Identifier
Pa, pascal[s]
psi
atm, atmosphere
mmHg, millimeter[s]_Hg
inHg, inch[es]_Hg

Volume

Unit Identifier
l, liter
cm³, cm^3, (cm)³
gallon
oz

Frequency

Unit Identifier
Hz, hertz, 1/s
kHz, kilohertz, kiloHz
MHz, megahertz, megaHz

Counting

Unit Identifier
1
count[s]
bit[s]
byte[s]