Here the units may be found either by looking under the in which they are used, (length energy etc.)  category 
or by picking one unit from an alphabetically ordered  list of units. 
There is a Summary Table of the most often required  Conversion Factors. 
There are NO units of currency.  
Finally there are some  notes on this material . 
A separate document covers the most  FAQ and other measures. 
Or, to get a Conversion Calculator, select required category
from this table
Conversion Calculators Any problems with any of these read the FAQ 

Length  Area  Volume  Mass  Temperature 
Feet & Inches  Angles  Pounds & Ounces  
Units of Alcohol  
Density  Pressure & Stress 
Speed  Fuel Consumption 
Power 
or ONE calculator just for Changing Prefixes  
Energy (Work)  Flow Rate by Mass by Volume 
Force  Torque  
Specific Energy by Mass by Volume (Calorific Value)  Spread Rate by Mass by Volume (including Rainfall) 
Concentration  
Line Density (inc. Textiles) 
Area Density  Acceleration  Viscosity Dynamic Kinematic  
Specific Heat Capacity by Mass by Volume  Heat Flux Density  Thermal Conductivity  Thermal Conductance  
There is a Selection of Other Calculators also available 
To change . .  into . .  do this . .  To change . .  into . .  do this . .  
acres  hectares  x 0.4047  kilograms  ounces  x 35.3  
acres  sq. kilometres  / 247  kilograms  pounds  x 2.2046  
acres  sq. metres  x 4047  kilograms  tonnes  / 1000 #  
acres  sq. miles  / 640 #  kilograms  tons (UK/long)  / 1016  
barrels (oil)  cu.metres  / 6.29  kilograms  tons (US/short)  / 907  
barrels (oil)  gallons (UK)  x 34.97  kilometres  metres  x 1000 #  
barrels (oil)  gallons (US)  x 42 #  kilometres  miles  x 0.6214  
barrels (oil)  litres  x 159  litres  cu.inches  x 61.02  
centimetres  feet  / 30.48 #  litres  gallons (UK)  x 0.2200  
centimetres  inches  / 2.54 #  litres  gallons (US)  x 0.2642  
centimetres  metres  / 100 #  litres  pints (UK)  x 1.760  
centimetres  millimetres  x 10 #  litres  pints (US liquid)  x 2.113  
cubic cm  cubic inches  x 0.06102  metres  yards  / 0.9144 #  
cubic cm  litres  / 1000 #  metres  centimetres  x 100 #  
cubic cm  millilitres  x 1 #  miles  kilometres  x 1.609  
cubic feet  cubic inches  x 1728 #  millimetres  inches  / 25.4 #  
cubic feet  cubic metres  x 0.0283  ounces  grams  x 28.35  
cubic feet  cubic yards  / 27 #  pints (UK)  litres  x 0.5683  
cubic feet  gallons (UK)  x 6.229  pints (UK)  pints (US liquid)  x 1.201  
cubic feet  gallons (US)  x 7.481  pints (US liquid)  litres  x 0.4732  
cubic feet  litres  x 28.32  pints (US liquid)  pints (UK)  x 0.8327  
cubic inches  cubic cm  x 16.39  pounds  kilograms  x 0.4536  
cubic inches  litres  x 0.01639  pounds  ounces  x 16 #  
cubic metres  cubic feet  x 35.31  
To change . .  into . .  do this . .  To change . .  into . .  do this . .  
square cm  sq. inches  x 0.1550  
feet  centimetres  x 30.48 #  square feet  sq. inches  x 144 #  
feet  metres  x 0.3048 #  square feet  sq. metres  x 0.0929  
feet  yards  / 3 #  square inches  square cm  x 6.4516 #  
fl.ounces (UK)  fl.ounces (US)  x 0.961  square inches  square feet  / 144 #  
fl.ounces (UK)  millilitres  x 28.41  square km  acres  x 247  
fl.ounces (US)  fl.ounces (UK)  x 1.041  square km  hectares  x 100 #  
fl.ounces (US)  millilitres  x 29.57  square km  square miles  x 0.3861  
gallons  pints  x 8 #  square metres  acres  / 4047  
gallons (UK)  cubic feet  x 0.1605  square metres  hectares  / 10 000 #  
gallons (UK)  gallons (US)  x 1.2009  square metres  x 10.76  
gallons (UK)  litres  x 4.54609 #  square metres  square yards  x 1.196  
gallons (US)  cubic feet  x 0.1337  square miles  acres  x 640 #  
gallons (US)  gallons (UK)  x 0.8327  square miles  hectares  x 259  
gallons (US)  litres  x 3.785  square miles  square km  x 2.590  
grams  kilograms  / 1000 #  square yards  square metres  / 1.196  
grams  ounces  / 28.35  tonnes  kilograms  x 1000 #  
hectares  acres  x 2.471  tonnes  tons (UK/long)  x 0.9842  
hectares  square km  / 100 #  tonnes  tons (US/short)  x 1.1023  
hectares  square metres  x 10000 #  tons (UK/long)  kilograms  x 1016  
hectares  square miles  / 259  tons (UK/long)  tonnes  x 1.016  
hectares  square yards  x 11 960  tons (US/short)  kilograms  x 907.2  
inches  centimetres  x 2.54 #  tons (US/short)  tonnes  x 0.9072  
inches  feet  / 12 #  yards  metres  x 0.9144 # 
Units are listed in alphabetical order. Scanning can be speeded up by selecting the initial letter of the unit from these individual letters or groups 
A  B  C  D  E  F  G  H  IJ  K  L  M N  O  PQ  R  S  T  UVW  XYZ 
The S I unit of length is the metre. To change any of these other units of length into their equivalent values in metres use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy. Where some uncertainty is indicated it means that a good idea of the size of the unit can be given but that a better value would depend upon knowing the period and/or culture in which the unit was being used.
Note than in matters concerned with land measurements, for the most accurate work, it is necessary to establish whether the US survey measures are being used or not.
angstroms divide by 10 000 000 000 # astronomical units x 149 598 550 000 barleycorns x 0.008 467 centimetres x 0.01 # chains (surveyors') x 20.1168 # cubits x (0.45 to 0.5) ells (UK) x 0.875 (but many variations) ems (pica) x 0.004 233 3 fathoms x 1.8288 # feet (UK and US) x 0.3048 # feet (US survey) x 0.304 800 609 6 furlongs x 201.168 # hands x 0.1016 # inches x 0.0254 # kilometres x 1000 # leagues x (4000 to 5000) light years x 9 460 500 000 000 000 links (surveyors') x 0.201 168 # metres [m] 1 microns (=micrometres) x 0.000 001 # miles (UK and US) x 1609.344 # miles (nautical) x 1852 # parsecs x 30 856 770 000 000 000 perch (=rods or poles) x 5.0292 # picas (computer) x 0.004 233 333 picas (printers') x 0.004 217 518 points (computer) x 0.000 352 777 8 points (printers') x 0.000 351 459 8 yards x 0.9144 # 
The S I unit of area is the square metre. To change any of these other units of area into their equivalent values in square metres use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy. Where some uncertainty is indicated it means that a good idea of the size of the unit can be given but that a better value would depend upon knowing the period and/or culture in which the unit was being used. Note than in matters concerned with land measurements, for the most accurate work, it is necessary to establish whether the US survey measures are being used or not.
acres x 4046.856 422 4 # ares x 100 # circular inches x 0.000 506 707 479 hectares x 10 000 # hides x 485 000 (with wide variations) roods x 1011.714 105 6 # square centimetres x 0.000 1 # square feet (UK and US) x 0.092 903 04 # square feet (US survey) x 0.092 903 411 613 square inches x 0.000 645 16 # square kilometres x 1 000 000 # square metres 1 square miles x 2 589 988.110 336 # square millimetres x 0.000 001 # squares (of timber) x 9.290 304 # square rods (or poles) x 25.292 852 64 # square yards x 0.836 127 36 # townships x 93 239 571.972 
The S I unit of volume is the cubic metre. However, this seems to be much less used than the litre (1000 litres = 1 cubic metre).To change any of these other units of volume into their equivalent values in litres use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
The litre. There can be some ambiguity about the size of the litre. When the metric system was introduced in the 1790's the litre was intended to match up with the volume occupied by 1 kilogram of pure water at a specified pressure and temperature. As the ability to measure things got better (by 100 years later) they found that there was a mismatch between the kilogram and the litre. As a result of this they had to redefine the litre (in 1901) as being 1.000028 cubic decimetres. Very handy!
This nonsense was stopped in 1964 when it was ruled that the word "litre" may be employed as a special name for the cubic decimetre, with the additional recommendation that for really accurate work, to avoid any possible confusion, the litre should not be used.
Here the litre is taken as being a cubic decimetre.
barrels (oil) x 158.987 294 928 # bushels (UK) x 36.368 72 # bushels (US) x 35.239 070 166 88 # centilitres x 0.01 # cubic centimetres x 0.001 # cubic decimetres 1 cubic decametres x 1 000 000 # cubic feet x 28.316 846 592 # cubic inches x 0.016 387 064 # cubic metres x 1000 # cubic millimetres x 0.000 001 # cubic yards x 764.554 857 984 # decilitres x 0.1 # fluid ounces (UK) x 0.028 413 062 5 # fluid ounces (US) x 0.029 573 529 562 5 # gallons (UK) x 4.546 09 # gallons, dry (US) x 4.404 883 770 86 # gallons, liquid (US) x 3.785 411 784 # litres [l or L] 1 litres (1901  1964) x 1.000 028 millilitres x 0.001 # pints (UK) x 0.568 261 25 # pints, dry (US) x 0.550 610 471 357 5 # pints, liquid (US) x 0.473 176 473 # quarts (UK) x 1.136 522 5 # quarts, dry (US) x 1.101 220 942 715 # quarts, liquid (US) x 0.946 352 946 # 
The S I unit of mass is the kilogram. To change any of these other units of mass into their equivalent values in kilograms use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
carats, metric x 0.000 2 # grains x 0.000 064 798 91 # grams x 0.001 # hundredweights, long x 50.802 345 44 # hundredweights, short x 45.359 237 # kilograms [kg] 1 ounces, avoirdupois x 0.028 349 523 125 # ounces, troy x 0.031 103 476 8 # pounds x 0.453 592 37 # slugs (or gpounds) x 14.593 903 stones x 6.350 293 18 # tons (UK or long) x 1016.046 908 8 # tons (US or short) x 907.184 74 # tonnes x 1000 # 
There have been five main temperature scales, each one being named after the person who invented it.
G D FAHRENHEIT (16861736) a German physicist, in about 1714 proposed the first practical scale. He called the freezingpoint of water 32 degrees (so as to avoid negative temperatures) and the boilingpoint 212 degrees.
R A F de REAUMUR (16731757) A French entomologist, proposed a similar scale in 1730, but set the freezingpoint at 0 degrees and the boilingpoint at 80 degrees. This was used quite a bit but is now obsolete.
Anders CELSIUS (17011744) a Swedish astronomer, proposed the 100degree scale (from 0 to 100) in 1742. This was widely adopted as the centigrade scale. But since grades and centigrades were also measures of angle, in 1947 it officially became the Celsius scale. Also, the S I system of units gives preference to naming units after people where possible.
William Thomson, 1st Lord KELVIN (18241907) a Scottish mathematician and physicist, worked with J P Joule  about 1862  to produce an absolute scale of temperature based on laws of heat rather than the freezing/boilingpoints of water. This work produced the idea of 'absolute zero', a temperature below which it was not possible to go. Its value is 273.15 degrees on the Celsius scale.
William J M RANKINE (18201872) a Scottish engineer and scientist, promoted the Kelvin scale in its Fahrenheit form, when the equivalent value of absolute zero is 459.67 degrees Fahrenheit.
Nowadays, while scientists use the KELVIN scale, the CELSIUS scale is the preferred scale in our everyday lives. However, the Fahrenheit scale is still widely used and there frequently is a need to be able to change from one to the other.
To change temperature given in Fahrenheit (F) to Celsius (C)Start with (F); subtract 32; multiply by 5; divide by 9; the answer is (C)To change temperature given in Celsius (C) to Fahrenheit (F)Start with (C); multiply by 9; divide by 5; add on 32; the answer is (F) 
Line density is a measure of mass per unit length. The S I compatible unit of line density is kilograms/metre. A major use of line density is in the textile industry to indicate the coarseness of a yarn or fibre. For that purpose the SI unit is rather large so the preferred unit there is the tex. (1 tex = 1 gram/kilometre) To change any of these other units of line density into their equivalent values in kilograms/metre use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
denier divide by 9 000 000 # drex divide by 10 000 000 # grams/centimetre divide by 10 # grams/kilometre (tex) divide by 1 000 000 # grams/metre divide by 1000 # grams/millimetre 1 kilograms/kilometre divide by 1000 # kilograms/metre 1 milligrams/centimetre divide by 10 000 # milligrams/millimetre divide by 1000 # ounces/inch x 1.116 125 ounces/foot x 0.093 01 pounds/inch x 17.858 pounds/foot x 1.488 164 pounds/yard x 0.496 055 pounds/mile x 0.000 281 849 tex divide by 1 000 000 # tons(UK)/mile x 0.631 342 tons(US)/mile x 0.563 698 tonnes/kilometre 1 
Density is the shortened term generally used in place of the more accurate description volumetric density.It is a measure of mass per unit volume. The S I compatible unit of density is kilograms/cubic metre. However, this a rather large unit for most purposes (iron is over 7000, wood is about 600 and even cork is over 200). A much more useful size of unit is kilograms/litre (for which the previous values then become 7, 0.6 and 0.2 respectively). This unit also has the great advantage of being numerically unchanged for grams/cubic centimetre and tonnes/cubic metre (or megagrams/cubic metre). To change any of these other units of density into their equivalent values in kilograms/litre use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
grains/gallon(UK) divide by 70 157 grains/gallon(US) divide by 58 418 grams/cubic centimetre 1 grams/litre divide by 1000 # grams/millilitre 1 kilograms/cubic metre divide by 1000 # megagrams/cubic metre 1 milligrams/millilitre divide by 1000 # milligrams/litre divide by 1 000 000 # kilograms/litre 1 ounces/cubic inch x 1.729 994 044 ounces/gallon(UK) x 0.006 236 023 ounces/gallon(US) x 0.007 489 152 pounds/cubic inch x 27.679 905 pounds/cubic foot x 0.016 018 463 pounds/gallon(UK) x 0.099 776 373 pounds/gallon(US) x 0.119 826 427 tonnes/cubic metre 1 tons(UK)/cubic yard x 1.328 939 184 tons(US)/cubic yard x 1.186 552 843 
International Table calorie = cal(IT) thermochemical calorie = cal(th) mean calorie = cal(mean) 15 degree C calorie = cal(15C) 20 degree C calorie = cal(20C). 
British thermal units(IT)x 1055.056 Btu (th) x 1054.350 Btu (mean) x 1055.87 calories  cal (IT) x 4.1868 #  cal (th) x 4.184 #  cal (mean) x 4.190 02  cal (15C) x 4.185 80  cal (20C) x 4.181 90 Calorie (food) x 4186 (approx.) centigrade heat units x 1900.4 ergs divide by 10 000 000 # foot poundsforce x 1.355 818 foot poundals x 0.042 140 gigajoules [GJ] x 1000 000 000 # horsepower hours x 2 684 520 (approx.) joules [J] 1 kilocalories (IT) x 4186.8 # kilocalories (th) x 4184 # kilogramforce metres x 9.806 65 # kilojoules [kJ] x 1000 # kilowatt hours [kWh] x 3 600 000 # megajoules [MJ] x 1 000 000 # newton metres [Nm] x 1 # therms x 105 500 000 (approx.) watt seconds [Ws] 1 watt hours [Wh] x 3600 # 
The S I unit of force is the newton. To change any of these other units of force into their equivalent values in newtons use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
dynes divide by 100 000 # kilograms force x 9.806 65 # kilonewtons [kN] x 1000 # kips x 4448.222 meganewtons [MN] x 1 000 000 # newtons [N] 1 pounds force x 4.448 222 poundals x 0.138 255 sthenes (=kN) x 1000 tonnes force x 9806.65 # tons(UK) force x 9964.016 tons(US) force x 8896.443 
Fuel consumption of any means of transport (car, aeroplane, ship etc.) that uses fuel is a measure giving the relationship between the distance travelled for an amount of fuel used. The most common example is the car where it is usually expressed (in Englishspeaking countries) in miles per gallon.
It could also be expressed in gallons per mile. However, for a car the latter method gives a rather small figure: 35 miles per gallon is about 0.0286 gallons per mile. In that case it would be better to give a figure for 100 miles, so it would be 2.86 gallons per 100 miles. That is the metric way of expressing fuel consumption  as litres per 100 kilometres.
From regular enquiries it appears that in real life people are using all sorts of ways of expressing their fuel consumption, so this section (unlike all the others) tries to cover as many ways as possible. All the values are given to an accuracy of 4 significant figures.
To change into miles per gallon (UK) miles per gallon (US) multiply by 0.833 miles per gallon (UK) miles per litre multiply by 0.22 miles per litre miles per gallon (UK) multiply by 4.546 miles per gallon (UK) kilometres per litre multiply by 0.354 miles per gallon (US) miles per gallon (UK) multiply by 1.2 miles per gallon (US) miles per litre multiply by 0.2642 miles per litre miles per gallon (US) multiply by 3.785 miles per gallon (US) kilometres per litre multiply by 0.4251 X miles per gallon gallons per 100 miles: divide 100 by X (both gallons must of the same type) X miles per gallon (UK) litres per 100 km: divide 282.5 by X X miles per gallon (US) litres per 100 km: divide 235.2 by X X km per litre litres per 100 km: divide 100 by X X miles per litre litres per 100 km: divide 62.14 by X 
Btu/hour x 0.293 071 Btu/minute x 17.584 267 Btu/second x 1055.056 calories/hour x 0.001 163 # calories/minute x 0.069 78 # calories/second x 4.1868 # ft lbforce/minute x 0.022 597 ft lbforce/second x 1.355 82 gigawatts [GW] x 1 000 000 000 horsepower (electric) x 746 # horsepower (metric) x 735.499 watts [W] 1 joules/hour divide by 3600 # joules/minute divide by 60 # joules/second 1 kilocalories/hour x 1.163 kilocalories/minute x 69.78 kgforce metres/hour x 0.002 724 kgforce metres/minute x 0.163 444 kilowatts [kW] x 1000 # megawatts [MW] x 1 000 000 # 
The S I unit of pressure is the pascal. The units of pressure are defined in the same way as those for stress  force/unit area. To change any of these other units of pressure (or stress) into their equivalent values in pascals use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy. Measures based on water assume a density of 1 kg/litre  a value which is rarely matched in the real world, though the error is small.
atmospheres x 101 325 # bars x 100 000 # centimetres of mercury x 1333.22 centimetres of water x 98.066 5 # feet of water x 2989.066 92 # hectopascals [hPa] x 100 # inches of water x 249.088 91 # inches of mercury x 3386.388 kgforce/sq.centimetre x 98 066.5 # kgforce/sq.metre x 9.806 65 # kilonewton/sq.metre x 1000 # kilopascal [kPa] x 1000 # kips/sq.inch x 6 894 760 meganewtons/sq.metre x 1 000 000 # metres of water x 9806.65 # millibars x 100 # pascals [Pa] 1 millimetres of mercury x 133.322 millimetres of water x 9.806 65 # newtons/sq.centimetre x 10 000 newtons/sq.metre 1 newtons/sq.millimetre x 1 000 000 # poundsforce/sq.foot x 47.880 poundsforce/sq.inch x 6894.757 poundals/sq.foot x 1.448 16 tons(UK)force/sq.foot x 107 252 tons(UK)force/sq.inch x 15 444 256 tons(US)force/sq.foot x 95 760 tons(US)force/sq.inch x 13 789 500 tonnesforce/sq.cm x 98 066 500 # tonnesforce/sq.metre x 9806.65 # 
The S I compatible unit of speed is metres/second. To change any of these other units of speed into their equivalent values in metres/second use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
centimetres/minute divide by 6000 # centimetres/second divide by 100 # feet/hour divide by 11 811 feet/minute x 0.005 08 # feet/second x 0.3048 # inches/minute divide by 2362.2 inches/second x 0.0254 # kilometres/hour divide by 3.6 # kilometres/second x 1000 # knots x 0.514 444 Mach number x 331.5 metres/hour divide by 3600 # metres/minute divide by 60 # metres/second [m/s] 1 miles/hour x 0.447 04 # miles/minute x 26.8224 # miles/second x 1609.344 # yards/hour divide by 3937 yards/minute x 0.015 24 # yards/second x 0.9144 # 
The spread rate of a substance is a measure of how much of it there is covering a unit area. The 'how much' can be measured by volume or by mass. The S I compatible unit of spread rate by mass is kilograms/square metre. It is also a measure of area density (mass/unit area) and is similar to  but not the same as  pressure, which is force/unit area. For the rainfall conversions a density of 1 kg/litre has been assumed. To change any of these other units of spread rate into their equivalent values in kilograms/square metre use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy. The conversion for rainfall assumes a density of 1 kg/litre which is accurate enough for all practical purposes.
grams/sq.centimetre x 10 # grams/sq.metre divide by 1000 # inches of rainfall x 2.54 kilograms/hectare divide by 10 000 # kilograms/sq.centimetre x 10 000 # milligrams/sq.metre divide by 1000 # millimetres of rainfall 1 kilograms/sq.metre 1 ounces/sq.foot x 0.305 152 ounces/sq.inch x 43.942 ounces/sq.yard divide by 49.494 pounds/acre divide by 8921.791 pounds/sq.foot x 4.882 428 pounds/sq.inch x 703.07 pounds/sq.yard x 0.542 492 tonnes/hectare divide by 10 # tons(UK)/acre divide by 3.982 942 tons(US)/acre divide by 4.460 896 
The spread rate of a substance is a measure of how much of it there is covering a unit area. The 'how much' can be measured by volume or by mass. The S I compatible unit of spread rate by volume is cubic metres/square metre. However, this is a rather large unit for most purposes and so litres/square metre is often preferred. To change any of these other units of spread rate into their equivalent values in litres/square metre use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
cubic feet/acre divide by 142.913 cubic inches/sq.yard divide by 51.024 cubic yards/sq.mile divide by 3387.577 cubic metres/hectare divide by 10 # cubic metres/sq.km divide by 1000 # cubic metres/sq.metre x 1000 # fl. ounces(UK)/sq.yard divide by 29.428 litres/square metre 1 gallons(UK)/acre divide by 890.184 gallons(US)/acre divide by 1069.066 gallons(UK)/hectare divide by 2199.692 gallons(US)/hectare divide by 2641.721 inches of rainfall x 25.4 # litres/hectare divide by 10 000 # millilitres/sq.metre divide by 1000 # millimetres of rainfall 1 
The S I compatible unit of torque is the newton metre. To change any of these other units of torque into their equivalent values in newton metres use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
dyne centimetres divide by 10 000 000 # gramforce centimetres x 0.000 098 066 5 # kgforce centimetres x 0.098 066 5 # kgforce metres x 9.806 65 # newton centimetres divide by 100 # newton metres [Nm] 1 ounceforce inches divide by 141.612 poundforce inches x 0.112 984 poundforce feet x 1.355 818 poundal feet x 0.042 140 ton(UK)force feet x 3 037.032 ton(US)force feet x 2 711.636 tonneforce metres x 9 806.65 # 


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