To represent a lot of the numbers I have used scientific notation. For instance the number 1300 is represented as 1.3E3. The "E" can be read as "times ten to the power of".

Each unit is written out in full before its abbreviation is used. Some units have superscripts in them, for instance m^{3}. This means cubic metres or "metres to the power of 3".

After some of the conversion factors is another conversion in brackets. This is the conversion for the same measuring system. For instance "foot (ft) to m: 3.048E-1 (12 in)" says that as well as one foot being 0.3048m it is also *exactly* 12in.

Taking the example of inch (in) to metre (m), the conversion factor is 2.54E-2 (or 0.0254):

- 12in in metres is 12*0.0254 = 0.305m

Converting the other way round is easy too - just divide by the conversion factor:

- 3m in inches is 3/0.0254 = 118in

To convert between (say) centimetres (cm) and inches (in) both conversion factors have to be used:

- 5cm in metres is 5*1E-2 = 0.05m
- 0.05m in inches is 0.05/2.54E-2 = 1.97in
- Therefore 5cm = 1.97in

A less involved way to do it would be to click on the title for the unit you are interested in to use the unit conversion form for that unit.

You may also like to read an explanation of the SI (metric) unit system.

millimetre (mm) to metre (m): 1E-3

centimetre (cm) to m: 1E-2

kilometre (km) to m: 1E3

inch (in) to m: 2.54E-2

foot (ft) to m: 3.048E-1 (12 in)

yard (yd) to m: 0.9144 exactly (3 ft)

fathom to m: 1.8288 (2 yd)

chain to m: 2.01168E1 (22 yd)

furlong to m: 2.01168E2 (10 chains, 220 yd)

cable - not precisely defined, 608ft (1/10 UK nautical mile) or 720 ft (120 fathoms)

mile to m: 1.609344E3 (1760 yd)

nautical mile (UK) to m: 1.853184E3 (6080 ft)

nautical mile (international) (n mile) to m: 1.852E3

league - not precisely defined, about 3 miles

astronomic(al) unit (AU) to m: 1.49597870E11

light year (l.y.) to m: 9.4607E15

parsec (pc) to m: 3.0857E16

mm^{2} to m^{2}: 1E-6

cm
^{2} to m^{2}: 1E-4

hectare to m^{2}: 1E4

km
^{2} to m^{2}: 1E6

in^{2} to m^{2}: 6.4516E-4

ft
^{2} to m^{2}: 9.290304E-2 (144 in^{2})

yd
^{2} to m^{2}: 8.3612736E-1 (9 ft^{2})

rood to m^{2}: 1.01171E3 (1210 yd^{2})

acre to m^{2}: 4.0468564224E3 (4840 yd^{2})

mile
^{2} to m^{2}: 2.58998811E6 (640 acres)

mm^{3} to m^{3}: 1E-9

cm
^{3} / ml to m^{3}: 1E-6

dm
^{3} / l to m^{3}: 1E-3

km
^{3} to m^{3}: 1E9

in^{3} to m^{3}: 1.6387064E-5

ft
^{3} to m^{3}: 2.8316846E-2 (1728 in^{3})

yd
^{3} to m^{3}: 7.64554858E-1 (27 ft^{3})

mile
^{3} to m^{3}: 4.168181825E9 (5451776000 yd^{3})

**UK**

minim (UKmin) to m^{3}: 5.91939E-8

fluid drachm (UK fl dr) to m^{3}: 3.55163E-6 (60 UKmin)

fluid ounce (UK fl oz) to m^{3}: 2.84131E-5 (8 UK fl dr)

gill to m^{3}: 1.42065E-4 (5 UK fl oz)

pint (UKpt) to m^{3}: 5.68261E-4 (4 gill)

quart (UKqt) to m^{3}: 1.13652E-3 (2 UKpt)

gallon (UKgal) to m^{3}: 4.54609E-3 (4 UKqt)

peck to m^{3}: 9.09218E-3 (2 UKgal)

bushel to m^{3}: 3.63687E-2 (4 peck)

**US (liquid)**

minim (USmin) to m^{3}: 6.16115E-8

fluid dram (US fl dr) to m^{3}: 3.69669E-6 (60 USmin)

liquid ounce (US liq oz) to m^{3}: 2.95735E-5 (8 US fl dr)

gill (gi) to m^{3}: 1.18294E-4 (4 US liq oz)

liquid pint (US liq pt) to m^{3}: 4.73176E-4 (4 gi)

liquid quart (US liq qt) to m^{3}: 9.46353E-4 (2 US liq pt)

gallon (USgal) to m^{3}: 3.785411784E-3 (4 US liq qt)

barrel to m^{3}: 1.58987E-1 (42 USgal)

**US (dry)**

dry pint (dry pt) to m^{3}: 5.50610E-4

dry quart (dry qt) to m^{3}: 1.10122E-3 (2 dry pt)

peck (pk) to m^{3}: 8.80977E-3 (8 dry qt)

bushel (bu) to m^{3}: 3.52391E-2 (4 pk)

dry barrel (bbl) to m^{3}: 1.15627E-1 (210 dry pt?)

milligram (mg) to kilogram (kg): 1E-6

gram (g) to kg: 1E-3

tonne to kg: 1E3 (1 megagram or Mg)

**UK (Avoirdupois)**

dram (dr) to kg: 1.77185E-3 (7000/256 grain)

ounce (oz) to kg: 2.83495E-2 (16 dr)

pound (lb) to kg: 0.45359237 exactly (16 oz and 7000 grain)

stone to kg: 6.35029 (14 lb)

slug (also gee pound) to kg: 1.45939E1

quarter (qr) to kg: 1.27006E1 (2 stone)

hundredweight (cwt) to kg: 5.08023E1 (4 qr and 112 lb)

ton (UK) (UKton) to kg: 1.016047E3 (20 cwt and 1.12 short ton)

**US**

dram (dr) to kg: 1.77185E-3 (as UK)

ounce (oz) to kg: 2.83495E-2 (as UK)

pound (lb) to kg: 0.45359237 (as UK)

short hundredweight (sh cwt) to kg: 4.53592E1 (100 lb)

short ton (sh tn / USton) to kg: 9.07185E2 (20 sh cwt)

**Apothecaries**

grain (gr in UK, no US symbol) to kg: 6.479891E-5 (1/7000 lb)

scruple to kg: 1.29598E-3 (20 grain)

drachm (dram in US) to kg: 3.88793E-3 (3 scruple)

apothecaries ounce (oz apoth in UK, oz ap in US) to kg: 3.11035E-2 (8 drachm and 1 oz tr)

**Troy**

grain to kg: as Apothecaries

pennyweight (dwt) to kg: 1.55517E-3 (24 grain)

troy ounce (oz tr) to kg: 3.11035E-2 (20 dwt)

troy pound (lb tr) to kg: 3.73242E-1 (12 oz tr)

km/h to m/s: 2.77778E-1

mph to m/s: 4.4704E-1

knots (international) (kn) to m/s: 5.14444E-1

Kelvin (K): *x* K

- = (
*x*-273.15) °C - = (5/4)(
*x*-273.15) °Réaumur - = (9/5)
*x*-459.67 °F - = (9/5)
*x*°Rankine

Celcius (also centigrade) (°C): *x* °C

- = (
*x*+273.15) K - = (5/4)
*x*°Réaumur - = (9/5)
*x*+32 °F - = (9/5)(
*x*+273.15) °Rankine

Réaumur (°R): *x* °Réaumur

- = (4/5)
*x*°C

Fahrenheit (°F): *x* °F

- = (5/9)(
*x*+459.67) K - = (5/9)(
*x*-32) °C - = (25/36)(
*x*-32) °Réaumur - = (
*x*+459.67) °Rankine

Rankine (°R): *x* °Rankine

- = (5/9)
*x*K - = (5/9)(
*x*-491.67) °C - = (25/36)(
*x*-491.67) °Réaumur - = (
*x*-459.67) °F

1 pascal (Pa) is equal to one newton per square metre (Nm^{-2} or kgm^{-1}s^{-2})

pound-force per square foot (lbf/ft^{2}) to Pa: 4.78803E1

millimetre of mercury (mmHg) to Pa: 1.33322E2 (1.00000 torr)

torr to Pa: 1.33322E2 (=101325/760) (1.00000 mmHg)

inch of water (inH20) to Pa: 2.49089E2

inch of mercury (inHg) to Pa: 3.38639E3

pound-force per square inch (lbf/in^{2}) to Pa: 6.89476E3 (144 lbf/ft^{2})

bar to Pa: 1E5

standard atmosphere (atm) to Pa: 1.01325E5 (760 torr)

1 joule (J) is equal to one newton metre (N.m)

electronvolt (eV) to J: 1.6021892E-19 (1*e**1V)

erg to J: 1E-7

foot pound-force (ft.lbf) to J: 1.35582

calorie (cal) to J: 4.1868

kilogram-force metre (kgf.m) to J: 9.80665

British Thermal Unit (Btu) to J: 1.05506E3

watt hour (W.h) to J: 3.6E3

kilowatt hour (kW.h) to J: 3.6E6

therm to J: 1.05506E8 (1E5 Btu)

1 watt (W) is equal to one joule per second (J/s or m^{2}kgs^{-3})

foot pound-force per second (ft.lbf/s) to W: 1.35582

kilogram-force metre per second (kgf.m/s) to W: 9.80665

horsepower (metric) to W: 7.35499E2 (75 kgf.m/s)

horsepower (hp) to W: 7.45700E2 (550 ft.lbf/s)

dyne (dyn) to newton (N): 1E-5

poundal (pdl) to N: 1.38255E-1

pound-force (lbf) to N: 4.44822

kilogram-force (kgf) or kilopond (kp) to N: 9.80665

sthène (sn) to N: 1E3

**Activity**

becquerel (Bq) is the SI unit of activity (of radionuclide), (equivalently s^{-1})

curie (Ci) to Bq: 3.7E10 (37 GBq)

**Dose**

sievert (Sv) is the SI unit of dose equivalent (equivalently m^{2}/s^{2}, J/kg, Nm/kg)

rem to Sv: 1E-2 (rem is Röntgen Equivalent Man)

**Exposure**

coulomb per kilogram (C/kg) is the SI unit of radiation exposure

röntgen to C/kg: 2.58E-4