There is an outline of the SI; a list of its basic defining standards and also some of its derived units; then another list of all the SI prefixes and some notes on conventions of usage.
There is a short historical note on measures generally; descriptions of the Metric system, the UK (Imperial) system with a statement on the implementation of 'metrication' in the UK, and the US system.
Finally there is a list of other sources concerned with the topic of measures and units (with a few references to currencies) and also some notes about this document.
It is based upon 7 principal units, 1 in each of 7 different categories -
Category Name Abbreviation Length metre m Mass kilogram kg Time second s Electric current ampere A Temperature kelvin K Amount of substance mole mol Luminous intensity candela cd
Definitions of these basic units are given.
Each of these units may take a prefix.
From these basic units many other units are derived and named.
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Note that prefixes may be used in conjunction with any of the above units.
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The SI allows the sizes of units to be made bigger or smaller by the use of appropriate prefixes. For example, the electrical unit of a watt is not a big unit even in terms of ordinary household use, so it is generally used in terms of 1000 watts at a time. The prefix for 1000 is kilo so we use kilowatts[kW] as our unit of measurement. For makers of electricity, or bigger users such as industry, it is common to use megawatts[MW] or even gigawatts[GW]. The full range of prefixes with their [symbols or abbreviations] and their multiplying factors which are also given in other forms is
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There are various rules laid down for the use of the SI and its units as well as some observations to be made that will help in its correct use.
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In England units of measurement were not properly standardised until the 13th century, though variations (and abuses) continued until long after that. For example, there were three different gallons (ale, wine and corn) up until 1824 when the gallon was standardised.
In the US A the system of weights and measured first adopted was that of the English, though a few differences came in when decisions were made at the time of standardisation in 1836. For instance, the wine-gallon of 231 cubic inches was used instead of the English one (as defined in 1824) of about 277 cubic inches. The US A also defined a separate dry gallon of about 269 cubic inches.
Even as late as the middle of the 20th century there were some differences in UK and US measures which were nominally the same. The UK inch measured 2.53998 cm while the US inch was 2.540005 cm. Both were standardised at 2.54 cm in July 1959.
In France the metric system officially started in June 1799 with the declared intent of being 'For all people, for all time'. The unit of length was the metre which was defined as being one ten-millionth part of a quarter of the earth's circumference. The production of this standard required a very careful survey to be done which took several years. However, as more accurate instruments became available so the 'exactness' of the standard was called into question. Later efforts were directed at finding some absolute standard based on an observable physical phenomenon. Over two centuries this developed into the S I. So maybe their original slogan was more correct than anyone could have foreseen then.
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1 yard = 0.9144 metres - same as US
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There have been three major Weights and Measures Acts in recent times (1963, 1976 and 1985) all gradually abolishing various units, as well re-defining the standards. All the Apothecaries' measures are gone, and of the Troy measures, only the ounce remains. Currently legislation has decreed that -
From the 1st October 1995, for economic, public health, public safety and administrative
purposes, only metric units are allowed EXCEPT that -
The following may continue to be used WITHOUT time limit -
The above only covers matters of trade.
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1 yard = 0.9144 metres - same as UK
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N - O - PQ - R - S - T - UVW - XYZ
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The SI 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.
The SI 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.
The SI 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 SI 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.
Line density is a measure of mass per unit length. The SI 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.
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 SI 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. 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.
The SI unit of energy or work is the joule. To change any of these other units of energy or work into their equivalent values in joules use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
The SI 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.
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 English-speaking countries) in miles per gallon. The SI unit of power is the watt. To change any of these other units of energy or work into their equivalent values in watts use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy.
The SI 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.
The SI 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.
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 SI 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 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 SI 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.
The SI 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.
Conversion Tables of Units for Science and Engineering by Ari L Horvath The Dent Dictionary of Measurement by Darton and Clark The Economist Desk Companion The Encyclopaedia Britannica World Weights and Measures The Weights and Measures of England by R D Connor British Weights and Measures by R E Zupko The World of Measurements by H Arthur Klein
Exchange rates for a wide range of currencies against any one single currency can be obtained from this program (in the U
International Standards Organisation [I S O]
This organisation (based in switzerland) is responsible for the world-wide publication of standards for just about anything for which standards can be set. Whilst none of the actual data is online, details of the work of ISO and the publications they produce are.
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The Prefixes of the S I
yotta [Y] 1 000 000 000 000 000 000 000 000 = 1024
zetta [Z] 1 000 000 000 000 000 000 000 = 1021
exa [E] 1 000 000 000 000 000 000 = 1018
peta [P] 1 000 000 000 000 000 = 1015
tera [T] 1 000 000 000 000 = 1012
giga [G] 1 000 000 000 (a thousand millions = a billion)
mega [M] 1 000 000 (a million)
kilo [k] 1 000 (a thousand)
1
milli [m] 0.001 (a thousandth)
micro [*] 0.000 001 (a millionth)
nano [n] 0.000 000 001 (a thousand millionth)
pico [p] 0.000 000 000 001 = 10-12
femto [f] 0.000 000 000 000 001 = 10-15
atto [a] 0.000 000 000 000 000 001 = 10-18
zepto [z] 0.000 000 000 000 000 000 001 = 10-21
yocto [y] 0.000 000 000 000 000 000 000 001 = 10-24
[*] the symbol used here is the Greek letter known as 'mu'
All of the SI prefixes are multiples or sub-multiples of 1000. However, these are inconvenient for many purposes and so hecta (x 100), deca (x 10), deci (x 0.1), and centi (x 0.01) are also used.
Conventions of Usage in the S I
A Brief History of Measurement
One of the earliest types of measurement concerned that of length. These measurements were usually based on parts of the body. A well documented example (the first) is the Egyptian cubit which was derived from the length of the arm from the elbow to the outstretched finger tips. By 2500 BC this had been standardised in a royal master cubit made of black marble (about 52 cm). This cubit was divided into 28 digits (roughly a finger width) which could be further divided into fractional parts, the smallest of these being only just over a millimetre.
Metric System of Measurements
Length Area
10 millimetres = 1 centimetre 100 sq. mm = 1 sq. cm
10 centimetres = 1 decimeter 10 000 sq. cm = 1 sq. metre
10 decimetres = 1 metre 100 sq. metres = 1 are
10 metres = 1 dekametre 100 ares = 1 hectare
10 dekametres = 1 hectometre 10 000 sq. metres = 1 hectare
10 hectometres = 1 kilometre 100 hectares = 1 sq. kilometre
1000 metres = 1 kilometre 1 000 000 sq. metres = 1 sq. kilometre
Capacity
10 millilitres = 1 centilitre
Volume 10 centilitree = 1 decilitre
1000 cu. mm = 1 cu. cm 10 decilitres = 1 litre
1 000 000 cu. cm = 1 cu. metre 1000 litres = 1 cu. metre
Mass
1000 grams = 1 kilogram
1000 kilograms = 1 tonne
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The UK (Imperial) System of Measurements
Length Area
12 inches = 1 foot 144 sq. inches = 1 square foot
3 feet = 1 yard 9 sq. feet = 1 square yard
22 yards = 1 chain 4840 sq. yards = 1 acre
10 chains = 1 furlong 640 acres = 1 square mile
8 furlongs = 1 mile
5280 feet = 1 mile
1760 yards = 1 mile Capacity
20 fluid ounces = 1 pint
Volume 4 gills = 1 pint
1728 cu. inches = 1 cubic foot 2 pints = 1 quart
27 cu. feet = 1 cubic yard 4 quarts = 1 gallon (8 pints)
Mass
437.5 grains = 1 ounce Troy Weights
16 ounces = 1 pound (7000 grains) 24 grains = 1 pennyweight
14 pounds = 1 stone 20 pennyweights = 1 ounce (480 grains)
8 stones = 1 hundredweight [cwt] 12 ounces = 1 pound (5760 grains)
20 cwt = 1 ton (2240 pounds)
Apothecaries' Measures Apothecaries' Weights
20 minims = 1 fl.scruple 20 grains = 1 scruple
3 fl.scruples = 1 fl.drachm 3 scruples = 1 drachm
8 fl.drachms = 1 fl.ounce 8 drachms = 1 ounce (480 grains)
20 fl.ounces = 1 pint 12 ounces = 1 pound (5760 grains)
The old Imperial (now UK) system was originally defined by three standard measures - the yard, the pound and the gallon which were held in London. They are now defined by reference to the SI measures of the metre, the kilogram and the litre. These equivalent measures are exact.
1 pound = 0.453 592 37 kilograms - same as US
1 gallon = 4.546 09 litres
Note particularly that the UK gallon is a different size to the US gallon so that NO liquid measures of the same name are the same size in the UK and US systems.
Also that the ton(UK) is 2240 pounds while a ton(US) is 2000 pounds. These are also referred to as a long ton and short ton respectively.
Metrication in the UK
may be used until 31st December 1999.
Sports are exempt from all of this, but most of them have (voluntarily) changed their relevant regulations into statements of equivalent metric measures.
Consenting adults (in private) may use any units they please.
The US System of Measurements
Most of the US system of measurements is the same as that for the UK. The biggest differences to be noted are in Capacity which has both liquid and dry measures as well as being based on a different standard - the US liquid gallon is smaller than the UK gallon. There is also a measurement known at the US survey foot. It is gradually being phased out as the maps and land plans are re-drawn under metrication. (The changeover is being made by putting 39.37 US survey feet = 12 metres)
Length Area
12 inches = 1 foot 144 sq. inches = 1 square foot
3 feet = 1 yard 9 sq. feet = 1 square yard
220 yards = 1 furlong 4840 sq. yards = 1 acre
8 furlongs = 1 mile 640 acres = 1 square mile
5280 feet = 1 mile 1 sq.mile = 1 section
1760 yards = 1 mile 36 sections = 1 township
Volume
1728 cu. inches = 1 cubic foot
27 cu. feet = 1 cubic yard
Capacity (Dry) Capacity (Liquid)
16 fluid ounces = 1 pint
2 pints = 1 quart 4 gills = 1 pint
8 quarts = 1 peck 2 pints = 1 quart
4 pecks = 1 bushel 4 quarts = 1 gallon (8 pints)
Mass
437.5 grains = 1 ounce Troy Weights
16 ounces = 1 pound (7000 grains) 24 grains = 1 pennyweight
14 pounds = 1 stone 20 pennyweights = 1 ounce (480 grains)
100 pounds = 1 hundredweight [cwt] 12 ounces = 1 pound (5760 grains)
20 cwt = 1 ton (2000 pounds)
Apothecaries' Measures Apothecaries' Weights
60 minims = 1 fl.dram 20 grains = 1 scruple
8 fl.drams = 1 fl.ounce 3 scruples = 1 dram
16 fl.ounces = 1 pint 8 drams = 1 ounce (480 grains)
12 ounces = 1 pound (5760 grains)
As with the UK system these measures were originally defined by physical standard measures - the yard, the pound, the gallon and the bushel.They are now all defined by reference to the SI measures of the metre, the kilogram and the litre. These equivalent measures are exact.
1 pound = 0.453 592 37 kilograms - same as UK
1 gallon (liquid) = 3.785 411 784 litres
1 bushel (dry) = 35.239 070 166 88 litres
Note particularly that the US gallon is a different size to the UK gallon so that NO liquid measures of the same name are the same size in the US and UK systems.
Also that the ton(US) is 2000 pounds while a ton(UK) is 2240 pounds. These are also referred to as a short ton and long ton respectively.
Categories of Units
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List of Units
The units are listed in alphabetical order but 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
A
B
C
D
E
F
G
H
IJ
K
L
M
N
O
PQ
R
S
T
UVW
XYZ
Length
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 0.3048 006 096
furlongs x 201.168 #
hands x 0.106 #
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 x 0.004 233 333
points (printers') x 0.000 352 777
yards x 0.9144 #
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Area
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
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Volume or Capacity
barrels (oil) x 158.987 294 928 #
bushels (UK) x 36.368 72 #
bushels, dry (US) x 35.239 070 166 88 #
centilitres x 0.01 #
cubic centimetres x 0.001 #
cubic decimetres 1
cubic dekametres 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 0.029 573 534 562 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
millitres 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 #
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Mass (or Weight)
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
kips x 453.592 37 #
newtons divide by 9.806 65 #
ounces, avoirdupois x 0.028 349 523 125 #
ounces, troy x 0.031 103 476 8 #
pounds x 0.453 592 37 #
slugs (or g-pounds) x 0.068 521
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 #
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Line density
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
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Density
grains/gallon(UK) divide by 70 156
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 #
milligrams/millitre 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
pounds/cubic inch x 27.679 904
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
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Energy or work
British thermal units divide by 1055.75 #
calories divide by 4.1868 #
centigrade heat units x 1900.4
ergs divide by 10 000 000 #
foot pounds-force x 1.355 817
foot poundals x 0.042 140
gigajoules [GJ] x 1000 000 000 #
horsepower hours x 2 684 520
joules [J] 1
kilocalories divide by 4186.8 #
kilogram-force 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 105 575 000 #
watt seconds [Ws] 1
watt hours [Wh] x 3600 #
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Force
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
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Fuel Consumption
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.
The rules below give a way of converting some of these different forms of measurement of fuel consumption. 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 4.456
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 miles, divide 282.5 by X
X miles per gallon (US) litres per 100 miles, divide 235.2 by X
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Power
Btu/hour x 0.293 071
Btu/minute x 17.584 263
Btu/second x 1055.055
calories/hour x 0.001 639
calories/minute x 0.069 78
calories/second x 4.1868
ft lb-force/minute x 0.022 597
ft lb-force/second x 1.355 82
gigawatts [GW] x 1 000 000 000
horsepower x 745.7
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
kg-force metres/hour x 0.002 724
kg-force metres/minute x 0.163 444
kiowatts [kW] x 1000 #
megawatts [MW] x 1 000 000 #
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Pressure or Stress
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 #
inches of water x 249.088 91 #
inches of mercury x 3386.388
kg-force/sq.centimetre x 98 066 5 #
kg-force/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 #
pounds-force/sq.foot x 47.880
pounds-force/sq.inch x 6894.757
poundals/sq.foot x 1.448 16
tons(UK)-force/sq.foot x 107 251
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
tonnes-force/sq.cm x 98 066 500 #
tonnes-force/sq.metre x 9806.65 #
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Speed
centimetres/minute divide by 6000 #
centimetres/second divide by 100 #
feet/hour divide by 11 811
feet/minute x 0.0005 08 #
feet/second x 0.3048 #
inches/minute divide by 2362.2
inches/second x 0.0254 #
kilometres/hour divide by 0.06 #
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 #
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Spread Rate (by mass)
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
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Spread Rate (by volume)
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 #
millitres/sq.metre divide by 1000 #
millimetres of rainfall 1
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Torque
ergs (= dyne cm) divide by 10 000 000 #
gram-force centimetres x 0.000 098 066 5 #
kg-force centimetres x 0.098 066 5 #
kg-force metres x 9.806 5 #
newton centimetres divide by 100 #
newton metres [Nm] 1
ounce-force inches divide by 141.612
pound-force inches x 0.112 984
pound-force 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
tonne-force metres x 9 806.65 #
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Other Sources
Macmillan Reference Books, London, 1986 (147 pages)
ISBN 0 333 40857 8
Probably the most comprehensive set of conversion factors in print, covering both old and modern units. There are 77 tables covering categories from Length to Radiation dosage. The Length table alone lists 107 units together with the conversion factors needed to change each one into metres.
J M Dent, London, 1994 (538 pages)
ISBN 0 460 861379
Very comprehensive coverage of all kinds of units (including currencies), ordered in conventional dictionary form, and giving several conversion factors.
Random Century, London, 1992 (272 pages)
ISBN 0 7126 9816 7
A handy compendium of units used in Science, Medicine, Engineering, Industry, Commerce, Finance and many other places, together with all the necessary conversion factors. There is also much other incidental (but related) information.
The modern E B has many references to units, but extensive use needs to be made of the index to find them all. It gives a wide selection of weights and measures from countries around the world and the appropriate conversion factors.
Statistical Office of the United Nations, New York 1955 (225 pages)
A very comprehensive survey of each country in the world (as it was then) from Aden to Zanzibar, giving the units used in each for Length, Area and Capacity with their British and Metric equivalents. There is an appendix on the measures used for selected commodities. Currencies are also given. The indexes are very thorough.
H M S O, London, 1987 (422 pages)
ISBN 0 460 86137 9
A scholarly and detailed account of the history of the development of the British (Imperial) system of weights and measures from the earliest times.
A history from Antiquity to the Seventeenth Century
The University of Wisconsin Press, 1977 [248 pages]
ISBN 0 299 07340 8
The actual history occupies only 100 pages. There is then an extensive list of the various units used in commerce, tables of many pre-Imperial units, a long list of pre-metric measures used in Europe together with their British and metric equivalents, and nearly 40 pages giving other sources.
Allen and Unwin, London, 1975 (736 pages)
ISBN 0 04 500024 7
A very readable and comprehensive account of the history of units used in measuring, from the earliest known beginnings and around the world.
On the World Wide Web
There is an interactive program (in Germany) which actually does the necessary calculation in order to change the value in one type of unit to its equivalent value in another type of unit. It also deals with a wide range of currencies.
Amongst many documents on offer there are -
Notes
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Publishing history
First placed online 19th June 1995.
Updates: nil