Energy / Work / Heat Converter
Convert between joules, calories, kilocalories, kilowatt-hours, BTU, electronvolts, therms, tons of TNT and every other unit of energy, work and heat.
1 joule = 0.000239005736 kilocalories
Most used energy units
- Joule J Base unit
- Kilocalorie kcal 1 kcal = 4,184 J
- Kilowatt-hour kWh 1 kWh = 3,600,000 J
- British thermal unit BTU 1 BTU = 1,055.0559 J
- Calorie cal 1 cal = 4.184 J
- Kilojoule kJ 1 kJ = 1,000 J
- Calorie (food) Cal 1 Cal = 4,184 J
- Electronvolt eV 1 eV = 1.6021766 × 10-19 J
- Watt-hour Wh 1 Wh = 3,600 J
- Foot-pound ft⋅lbf 1 ft⋅lbf = 1.3558179 J
- Megajoule MJ 1 MJ = 1,000,000 J
- Therm thm 1 thm = 105,480,400 J
Popular energy conversions
- Kilocalories to kilojoules 1 kcal = 4.184 kJ
- Kilojoules to kilocalories 1 kJ = 0.2390057 kcal
- Joules to calories 1 J = 0.2390057 cal
- Calories to joules 1 cal = 4.184 J
- Kilowatt-hours to joules 1 kWh = 3,600,000 J
- Joules to kilowatt-hours 1 J = 2.7777778 × 10-7 kWh
- British thermal units to kilowatt-hours 1 BTU = 0.0002930711 kWh
- Kilowatt-hours to British thermal units 1 kWh = 3,412.142 BTU
- Kilocalories to calories 1 kcal = 1,000 cal
- Calories to kilocalories 1 cal = 0.001 kcal
- British thermal units to joules 1 BTU = 1,055.056 J
- Joules to electronvolts 1 J = 6.2415091 × 1018 eV
- Electronvolts to joules 1 eV = 1.6021766 × 10-19 J
- Therms to kilowatt-hours 1 thm = 29.30011 kWh
- Foot-pounds to joules 1 ft⋅lbf = 1.355818 J
- Kilojoules to joules 1 kJ = 1,000 J
- Megajoules to kilowatt-hours 1 MJ = 0.2777778 kWh
- Kilowatt-hours to megajoules 1 kWh = 3.6 MJ
- Tons of TNT to joules 1 t TNT = 4,184,000,000 J
- Calories (food) to kilojoules 1 Cal = 4.184 kJ
What is energy?
Energy is the capacity to do work or produce heat. It comes in many forms (the chemical energy in food and fuel, electrical energy, the kinetic energy of moving things, heat) and each field has kept its own favorite unit: nutritionists count calories, utilities bill in kilowatt-hours, heating engineers use BTU and therms, physicists use electronvolts and explosives are rated in tons of TNT.
The SI unit of energy is the joule, the work done by a force of one newton moving something one meter. It is a small amount: lifting an apple one meter takes about one joule, and a single food Calorie is 4,184 joules.
Energy and power are often confused. Power is the rate of using energy: a 100-watt bulb uses 100 joules every second, and running it for 10 hours uses one kilowatt-hour. For rates, see the power converter.
Common energy equivalents
- 1 kilocalorie (food Calorie) = 4,184 J = 4.184 kJ
- 1 kilowatt-hour = 3,600,000 J = 3.6 MJ ≈ 3,412 BTU ≈ 860 kcal
- 1 BTU ≈ 1,055 J ≈ 252 calories
- 1 therm = 100,000 BTU ≈ 29.3 kWh
- 1 electronvolt ≈ 1.602 × 10⁻¹⁹ J
- 1 ton of TNT = 4.184 GJ ≈ 1,162 kWh
- 1 barrel of oil equivalent ≈ 6.12 GJ ≈ 1,700 kWh
Calories and Calories
The "Calories" on food labels are kilocalories: one food Calorie (with a capital C) is 1,000 small calories, or 4,184 joules. Europe and Australia label food in kilojoules as well: a 250 kcal snack is about 1,046 kJ.
Several slightly different small calories exist. The thermochemical calorie (4.184 J) is used in chemistry and nutrition; the International Table calorie (4.1868 J) in engineering and steam tables. The difference is under 0.1%.
Energy units from smallest to largest
Every proportional energy unit on the site, ordered by size and expressed in joules.
- Hertz (energy) 6.62607 × 10-34 J
- Kelvin (energy) 1.380649 × 10-23 J
- Wavenumber (energy) 1.986446 × 10-23 J
- Millielectronvolt 1.602177 × 10-22 J
- Kilojoule per mole 1.660539 × 10-21 J
- Kilocalorie per mole 6.947695 × 10-21 J
- Electronvolt 1.602177 × 10-19 J
- Rydberg 2.179872 × 10-18 J
- Hartree 4.359745 × 10-18 J
- Kiloelectronvolt 1.602177 × 10-16 J
- Megaelectronvolt 1.602177 × 10-13 J
- Gigaelectronvolt 1.602177 × 10-10 J
- Nanojoule 1 × 10-9 J
- Erg 1 × 10-7 J
- Teraelectronvolt 1.602177 × 10-7 J
- Microjoule 0.000001 J
- Petaelectronvolt 0.000160218 J
- Millijoule 0.001 J
- Inch-ounce 0.00706155 J
- Foot-poundal 0.0421401 J
- Cubic centimeter-atmosphere 0.101325 J
- Inch-pound 0.112985 J
- Exaelectronvolt 0.160218 J
- Joule 1 J
- Foot-pound 1.35582 J
- Milliwatt-hour 3.6 J
- 20 °C calorie 4.182 J
- Calorie 4.184 J
- 15 °C calorie 4.1855 J
- International Table calorie 4.1868 J
- Mean calorie 4.19002 J
- Kilogram-force meter 9.80665 J
- Liter-atmosphere 101.325 J
- Cubic foot-psi 195.238 J
- Kilojoule 1,000 J
- Thermochemical BTU 1,054.35 J
- 60 °F BTU 1,054.68 J
- 59 °F BTU 1,054.8 J
- British thermal unit 1,055.06 J
- Mean BTU 1,055.87 J
- 39 °F BTU 1,059.67 J
- Celsius heat unit 1,899.1 J
- Cubic foot-atmosphere 2,869.2 J
- Watt-hour 3,600 J
- Kilocalorie 4,184 J
- Calorie (food) 4,184 J
- Gram of TNT 4,184 J
- AA battery 10,000 J
- Smartphone battery 54,000 J
- Banana (food energy) 439,320 J
- Megajoule 1,000,000 J
- Thousand BTU 1,055,060 J
- Cubic foot of natural gas 1,094,090 J
- Big Mac (food energy) 2,355,590 J
- Metric horsepower-hour 2,647,800 J
- Horsepower-hour 2,684,520 J
- Kilowatt-hour 3,600,000 J
- Megacalorie 4,184,000 J
- Kilogram of TNT 4,184,000 J
- Thermie 4,185,500 J
- Liter of gasoline 34,200,000 J
- Cubic meter of natural gas 38,300,000 J
- Therm 105,480,000 J
- EC therm 105,506,000 J
- Gallon of gasoline equivalent 121,320,000 J
- Gallon of diesel equivalent 144,945,000 J
- Gigajoule 1,000,000,000 J
- Lightning bolt 1,000,000,000 J
- Dekatherm 1,054,800,000 J
- Million BTU 1,055,060,000 J
- Planck energy 1,956,100,000 J
- Megawatt-hour 3,600,000,000 J
- Ton of TNT 4,184,000,000 J
- Gigacalorie 4,186,800,000 J
- Barrel of oil equivalent 6,117,860,000 J
- Tonne of coal equivalent 29,307,600,000 J
- Tonne of oil equivalent 41,868,000,000 J
- Terajoule 1,000,000,000,000 J
- Gigawatt-hour 3,600,000,000,000 J
- Kiloton of TNT 4,184,000,000,000 J
- Thousand barrels of oil equivalent 6,117,860,000,000 J
- Kilotonne of oil equivalent 41,868,000,000,000 J
- Hiroshima bomb 63,000,000,000,000 J
- Petajoule 1 × 1015 J
- Terawatt-hour 3.6 × 1015 J
- Megaton of TNT 4.184 × 1015 J
- Million barrels of oil equivalent 6.117863 × 1015 J
- Million tonnes of oil equivalent 4.1868 × 1016 J
- Tsar Bomba 2.1 × 1017 J
- Exajoule 1 × 1018 J
- Quad 1.055056 × 1018 J
- Petawatt-hour 3.6 × 1018 J
- Gigaton of TNT 4.184 × 1018 J
- US annual energy consumption 1 × 1020 J
- World annual energy consumption 6.2 × 1020 J
- Zettajoule 1 × 1021 J
- Q unit 1.055056 × 1021 J
- Solar luminosity second 3.828 × 1026 J
- Foe 1 × 1044 J
All 99 energy units
Metric (SI)
- Exajoules
- Gigajoules
- Joules
- Kilojoules
- Megajoules
- Microjoules
- Millijoules
- Nanojoules
- Petajoules
- Terajoules
- Zettajoules
Electrical
Calories
- 15 °C calories
- 20 °C calories
- Calories
- Calories (food)
- Gigacalories
- International Table calories
- Kilocalories
- Mean calories
- Megacalories
- Thermies
BTU & therms
- 39 °F BTUs
- 59 °F BTUs
- 60 °F BTUs
- British thermal units
- Celsius heat units
- Dekatherms
- EC therms
- Mean BTUs
- Million BTU
- Q units
- Quads
- Therms
- Thermochemical BTUs
- Thousand BTU
Mechanical
- Cubic centimeter-atmospheres
- Cubic foot-atmospheres
- Cubic foot-psis
- Ergs
- Foot-pounds
- Foot-poundals
- Horsepower-hours
- Inch-ounces
- Inch-pounds
- Kilogram-force meters
- Liter-atmospheres
- Metric horsepower-hours
Atomic & physics
- Electronvolts
- Exaelectronvolts
- Foes
- Gigaelectronvolts
- Hartrees
- Hertz (energy)
- Kelvins (energy)
- Kilocalories per mole
- Kiloelectronvolts
- Kilojoules per mole
- Megaelectronvolts
- Millielectronvolts
- Petaelectronvolts
- Planck energies
- Rydbergs
- Teraelectronvolts
- Wavenumbers (energy)
Fuel & explosive equivalents
- Barrels of oil equivalent
- Cubic feet of natural gas
- Cubic meters of natural gas
- Gallons of diesel equivalent
- Gallons of gasoline equivalent
- Gigatons of TNT
- Grams of TNT
- Kilograms of TNT
- Kilotons of TNT
- Kilotonnes of oil equivalent
- Liters of gasoline
- Megatons of TNT
- Million barrels of oil equivalent
- Million tonnes of oil equivalent
- Thousand barrels of oil equivalent
- Tons of TNT
- Tonnes of coal equivalent
- Tonnes of oil equivalent
Everyday comparisons
Frequently asked questions
How many joules are in a calorie?
A (thermochemical) calorie is exactly 4.184 joules. A food Calorie (kilocalorie) is 4,184 joules.
How many kWh is a BTU?
One BTU is about 0.000293 kWh; one kWh is about 3,412 BTU.
What is the difference between energy and power?
Energy is an amount (joules, kWh); power is a rate (watts). A 2 kW heater running for 3 hours uses 6 kWh of energy.
How much energy is a kilowatt-hour?
3.6 million joules: enough to run a 100 W bulb for 10 hours, boil about 11 liters of water from room temperature, or drive an electric car about 6–7 km.