Whole Farm > Weight & Measurements
Updated June, 2021
File C6-86
Energy Measurements and Conversions
Common Prefixes and Abbreviations
Deka = ten
Hecto = hundred
Kilo = thousand
Mega = million
Giga = billion
Tera = trillion
British thermal unit (Btu)
Kilocalories (kcal)
Kilojoule (kJ)
Kilowatt (kW)
Megawatt (MW)
Gigawatt (GW)
Terawatt (TW)
Watthour (Wh)
Kilowatthour (kWh)
Megawatthour (MWh)
Gigawatthour (GWh)
Terawatthour (TWh)
1 metric ton = 2,204.62 pounds
1 metric ton = 1.1023 short tons
1 kiloliter = 6.2898 barrels (crude oil)
1 barrel = 42 gallons
1 kiloliter = 1 cubic meter
British Thermal Unit (Btu) Measurements and Conversions
Approximate definition: A British thermal unit is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
1 Btu = 252 International Table calories
1 calorie = .00397 Btu
1 Btu = .252 kilocalories
1 kilocalorie = 3.968 Btu
1 Btu = 1,055.05585 joules
1 Btu = 1.055 kilojoules
1 kilojoule = .947817 Btu
1 therm = 100,000 Btu
1 dekatherm = 10 therms
1 dekatherm = 1 million Btu
1 kilowatthour = 3,412 Btu
1 horsepower = 2,545 Btu per hour
Joule Measurements and Conversions
Approximate definition: the energy required to lift one newton (102 g or a small apple) one meter against Earth’s gravity.
1 joule = .0009478 Btu
1 Btu = 1,055.05585 joules
1 kilojoule = 1,000 joules
1 kilojoule = .947817 Btu
1 Btu = 1.055 kilojoules
1 kilojoule = .239 kilocalories
1 kilocalorie = 4.1868 kilojoules
1 watthour = 3,600 joules
1 kilowatthour = 3.6 megajoules
1 megajoule = 1 million joules
1 terajoule = 1 million megajoules
Electricity Measurements and Conversions
WattApproximate definition: A human climbing a flight of stairs is doing work at the rate of about 200 watts.
Source: convertworld.com
1 watt = 1 joule per second
1 watt = 3.412 Btu per hour
1 Btu per hour = .293 watts
1 kilowatt = 1,000 watts
1 kilowatt = 3,412 Btu per hour
1 kilowatt = 1.341 horsepower (electric)
1 horsepower (electric) = .7457 kilowatts
1 megawatt = 1 million watts
1 gigawatt = 1 billion watts
1 terawatt = 1 trillion watts
1 gigawatt = 1 million kilowatts
Approximate definition: One watthour is the amount of (usually electrical) energy expended by a one-watt load (e.g., light bulb) drawing power for one hour.
Source: US Department of Energy
1 watt second = 1 joule
1 watt minute = 60 joules
1 watthour = 3,600 joules
1 watthour = 3.6 kilojoules
1 kilowatthour = 3.6 megajoules
1 megajoule = .278 kilowatthours
1 kilowatthour = 3,412 Btu
1 kilowatthour = 860 kilocalories
1 kilowatthour = 3,600 kilojoules
1 kilowatthour = 1.341 horsepower hours (electric)
1 horsepower hour (electric) = .7457 kilowatthours
1 kilowatthour = 1 thousand watthours
1 megawatthour = 1 million watthours
1 gigawatthour = 1 billion watthours
1 terawatthour = 1 trillion watthours
1 gigawatthour = 1 million kilowatthours
1 terawatthour = 1 billion kilowatthours
1 terawatthour = 1 million megawatthours
Power Measurements and Conversions
1 Btu per second = 1.055 kilowatts
1 Btu per second = 1.415 horsepower (electric)
1 Btu per second = 1.434 horsepower (metric)
1 Btu per second = .252 kilocalories per second
1 kilowatt = .9478 Btu per second
1 kilowatt = 1.341 horsepower (electric)
1 kilowatt = 1.3596 horsepower (metric)
1 kilowatt = .2388 kilocalories per second
1 horsepower (electric) = .7457 kilowatts
1 horsepower (electric) = 1.014 horsepower (metric)
1 horsepower (electric) = .1782 kilocalories per second
1 horsepower (electric) = .7068 Btu per second
1 horsepower (metric) = .9863 horsepower (electric)
1 horsepower (metric) = .7355 kilowatts
1 horsepower (metric) = .1757 kilocalories per second
1 horsepower (metric) = .6971 Btu per second
References and Conversion Calculators
Biomass Energy Datebook, US Department of Energy
Energy Information Administration (EIA)
Units and Calculators Explained, EIA
The International System of Units (SI) - Conversion Factors for General Use
Conversion Calculator for Units of Power, Oklahoma Local Technical Assistance Program (LTAP)
Note: This document includes units of measurement that may have more than one definition. Refer to sources listed for more detailed information.
Don Hofstrand, retired extension value added agriculture specialist, agdm@iastate.edu