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All conversions are based on the definitions, assumptions and the values of standard variables presented below.
GENERAL
Variable
|
Value
|
Meaning
|
Notes
|
StandardGravity
|
9.80665
|
Standard Gravity is 9.80665 m/s2
|
Exact definition
|
LENGTH
Variable
|
Value
|
Meaning
|
Notes
|
OneFootEqualsInches
|
12
|
1 ft = 12 in
|
Exact definition
|
OneInchEqualsMeters
|
0.0254
|
1 in = 0.0254 m
|
Exact definition
|
OneYardEqualsMeters
|
0.9144
|
1 yard = 91.44 cm
|
Exact definition
|
OneLandMileEqualsYards
|
1760
|
1 land mile = 1760 yards
|
Exact definition
|
OneNauticalMileEqualsMeters
|
1852
|
1 nautical mile = 1852 m
|
Exact definition
|
OneAngstromEqualsMeters
|
0.0000000001
|
1 angstrom = 1010 m
|
Exact definition
|
OneLightYearEqualsMeters
|
9460730472580800
|
1 light-year = 9,460,730,472,580,800 m
|
Exact definition
|
OneAstronomicalUnitEqualsMeters
|
149597870700
|
1 AU = 149597870700 m
|
Exact definition
|
OneFathomEqualsFeet
|
6
|
1 fathom = 6 feet
|
Exact definition
|
OneChainEqualsFeet
|
66
|
1 chain (ch) = 66 feet
|
Exact definition
|
OneParsecEqualsAU
|
648000 / π
|
1 parsec = 648000/π Astronomical Units
|
Exact definition
|
AREA
Variable
|
Value
|
Meaning
|
Notes
|
OneSquareMetreEqualsBarns
|
1028
|
1 barn = 10-28 m2
|
Exact definition
|
OneStremmaEqualsSquareMeters
|
1000
|
1 stremma = 1000 m2
|
Exact definition
|
OneSqMileEqualsAcres
|
640
|
1 acre = 1/640 sq. mile
|
Exact definition
|
MASS and FORCE
Variable
|
Value
|
Meaning
|
Notes
|
OneLbmEqualsKg
|
0.45359237
|
1 lbm = 0.45359237 kg
|
Exact definition
|
OneGrainEqualsmg
|
64.79891
|
1 grain = 64.79891 milligrams
|
Exact definition
|
OneTroyOunceEqualskg
|
0.0311034768
|
1 ozt = 0.0311034768 kg
|
Exact definition
|
OneLongTonEqualsGrams
|
1016046.9088
|
1 long ton = 1,016,046.9088 grams
|
Exact definition
|
OneShortTonEqualsLbm
|
2000
|
1 short ton = 2000 lbm
|
Exact definition
|
OneOunceEqualsGram
|
28.349523125
|
1 ounce = 28.349523125 g
|
Exact definition
|
OnePennyweightEqualsGrains
|
24
|
1 pennyweight = 24 grains
|
Exact definition
|
TIME
Variable
|
Value
|
Meaning
|
Notes
|
OneMinuteEqualsSeconds
|
60
|
1 min = 60 s
|
Exact definition
|
OneHourEqualsMinutes
|
60
|
1 hour = 60 min
|
Exact definition
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OneDayEqualsHours
|
24
|
1 day = 24 h
|
Exact definition
|
OneWeekEqualsDays
|
7
|
1 week = 7 days
|
Exact definition
|
OneJulianYearEqualsDays
|
365.25
|
1 Julian year = 365.25 days
|
Exact definition
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OneCommonYearEqualsDays
|
365
|
1 Common year = 365 days
|
Exact definition
|
OneDecadeEqualsYears
|
10
|
1 decade = 10 years
|
Exact definition
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OneCenturyEqualsYears
|
100
|
1 century = 100 years
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Exact definition
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VOLUME
Variable
|
Value
|
Meaning
|
Notes
|
OneImperialGallonEqualsLitres
|
4.54609
|
1 imperial gallon = 4.54609 litres
|
Exact definition
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OneUSGallonEqualsCubicInches
|
231
|
1 US gallon = 231 cubic inches
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Exact definition
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OneImperialPintEqualsImperialFluidOunces
|
20
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1 imperial pint = 20 imperial fluid ounces
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Exact definition
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OneUSPintEqualsUSFluidOunces
|
16
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1 US pint = 16 US fluid ounces
|
Exact definition
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OneGallonEqualsPints
|
8
|
1 gallon = 8 pints *
|
Exact definition
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OneGallonEqualsQuarts
|
4
|
1 gallon = 4 quarts *
|
Exact definition
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OneFluidOunceEqualsMinims
|
480
|
1 fluid ounce = 480 minims *
|
Exact definition
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OneFluidOunceEqualsFluidDrams
|
8
|
1 fluid ounce = 8 fluid drams *
|
Exact definition
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OneTroyPoundEqualsTroyOunces
|
12
|
1 troy pound = 12 troy ounces
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Exact definition
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* Applies to both imperial and US units (gallon, pint, quart, fluid ounce, minim, etc).
SPEED
Variable
|
Value
|
Meaning
|
Notes
|
SpeedOfLightInMeterPerSecond
|
299792458
|
c = 299792458 m/s
|
Exact definition
According to the 2006 version of the SI manual and the 2019 redefinition of the SI base units
|
PRESSURE
Variable
|
Value
|
Meaning
|
Notes
|
OneBarEqualsPascal
|
100000
|
1 bar = 100000 Pa
|
Exact definition
|
OnemmHgEqualsPascal
|
133.322387415
|
1 mm of mercury = 133.322387415 Pa
|
Exact definition
|
OneStandardAtmosphereEqualsPascal
|
101325
|
1 standard atmosphere = 101325 Pa
|
Exact definition
|
OneAtmosphereEqualsTorr
|
760
|
1 Torr = 1/760 standard atmosphere
|
Exact definition
|
COMPUTER
Variable
|
Value
|
Meaning
|
Notes
|
OneByteEqualsBits
|
8
|
1 byte = 8 bits
|
Exact definition
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ENERGY
Variable
|
Value
|
Meaning
|
Notes
|
OneFoeEqualsJoules
|
1044
|
1 foe = 1044 J
|
Exact definition
|
OneThermEqualsBTU
|
105
|
1 therm = 100,000 BTU
|
Exact definition
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OneCalTHEqualsJoules
|
4.184
|
1 thermochemical calorie = 4.184 J
|
Exact definition
|
OneCalITEqualsJoules
|
4.1868
|
1 Int. Steam Table calorie (1956) = 4.1868 J
|
Exact definition
The Fifth International Conference on the Properties of Steam (London, July 1956) defined the International Table calorie as 4.1868 J
|
OneCal15EqualsJoules
|
4.1855
|
One 15 °C calorie ≈ 4.1855 J
|
The amount of energy required to warm one gram of air-free water from 14.5 to 15.5 °C at standard atmospheric pressure. Experimental values of this calorie ranged from 4.1852 to 4.1858 J. The CIPM in 1950 (Comité international des poids et mesures (International Committee for Weights and Measures) 1950; PV, 1950, 22, 79–80) published a mean experimental value of 4.1855 J, noting an uncertainty of 0.0005 J.
|
OneTonOfTNTEqualsCaloriesTH
|
109
|
1 ton TNT ≈ 109 thermochemical calories
|
Can be considered an approximate definition
|
OneBTUITEqualsJoules
|
OneLbmEqualsKg * 1000 * 5 / 9 * OneCalITEqualsJoules = 1055.05585262
|
1 BTU(IT) = 1055.05585262 J
|
The most widespread BTU uses the International Steam Table (IT) calorie, which was defined by the Fifth International Conference on the Properties of Steam (London, July 1956) to be exactly 4.1868 J. Therefore, the exact conversion factor for the International Table Btu is 1055.05585262 J, as shown in the calculation.
|
OneBTUTHEqualsJoules
|
OneLbmEqualsKg * 1000 * 5 / 9 * OneCalTHEqualsJoules = 9489.1523804 / 9 ≈ 1054.350264488889
|
1 BTU(TH) = 9489.1523804 / 9 J ≈ 1054.350264488889 J
|
It is based on the definition of the thermochemical calorie, which is equal to 4.184 J. The calculation is similar to the one for the IT case.
|
OneBTU59FEqualsJoules
|
1054.804
|
1 BTU(59) = 1054.804
|
59 °F (15 °C) is the most widely used reference temperature for BTU definition in the US.
Different values can be found in the literature. This value is the one most commonly used. See:
https://en.wikipedia.org/wiki/British_thermal_unit (reporting 1054.80 J)
https://physics.nist.gov/cuu/pdf/sp811.pdf (reporting 1054.80 J)
|
ElementaryCharge
|
1.602176634×10-19
|
1 electronvolt = 1.602176634×10-19 J
|
Exact definition
According to the 2019 redefinition of the SI base units
|
Notes:
•A calorie is a unit of energy which was defined as the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. The amount depends on the atmospheric pressure and the starting temperature, and different choices of these parameters have resulted in several different definitions of the unit, as the temperature response of water to heat energy is non-linear (the change in temperature of a water mass caused by adding a certain amount of heat to it will be a function of the water's initial temperature). Therefore, the precise equivalence between calories and joules has varied over the years, but in thermochemistry and nutrition it is now generally assumed that one thermochemical calorie is equal to exactly 4.184 J.
•A BTU was originally defined as the amount of heat required to raise the temperature of 1 avoirdupois pound of liquid water by 1 degree Fahrenheit at a constant pressure of one atmospheric unit. There are several different definitions of the BTU that differ slightly. This reflects the fact that the temperature change of a mass of water due to the addition of a specific amount of heat (calculated in energy units, usually joules) depends slightly upon the water's initial temperature. Definitions of the BTU based on different water temperatures vary by up to 0.5%. Source: https://en.wikipedia.org/wiki/British_thermal_unit
POWER
Variable
|
Value
|
Meaning
|
Notes
|
OneHorsepowerMechanicalHPEquals_ftlbf_per_min
|
33000
|
1 Mechanical horsepower = 33,000 ft·lbf/min
|
Exact definition
|
OneHorsepowerMetricPSEquals_kgfm_per_s
|
75
|
1 Metric horsepower = 75 kgf·m/s
|
Exact definition
|
OneHorsepowerElectricalEquals_Watt
|
746
|
1 Electrical horsepower = 746 W
|
Exact definition
|
TEMPERATURE
Unit (symbol)
|
Definition
|
Celcius (°C)
|
-
|
Fahrenheit (°F)
|
[°F] = [°C] × 9/5 + 32
|
Kelvin (K)
|
[K] = [°C] + 273.15
|
Rankine (°R)
|
[°R] = ([°C] + 273.15) × 9/5
|
Delisle (°D)
|
[°De] = (100 - [°C]) × 3/2
|
Newton (°N)
|
[°N] = [°C] × 33/100
|
Réaumur (°Ré)
|
[°Ré] = [°C] × 4/5
|
Rømer (°Rø)
|
[°Rø] = [°C] × 21/40 + 7.5
|
|