Energy Converter
Enter an energy value below to convert between Joules, calories, kilowatt-hours, and BTUs.
Convert Energy
Enter a value and select the units to convert between kilojoules, kilocalories, and kilowatt-hours.
You can change the units using the dropdowns above or click on a unit button.
Common Energy Reference Points
Here are some common energy values in Kilojoule (kJ), Kilocalorie (Food Calorie) (kcal), and Kilowatt-hour (kWh). Click any preset value or arrow to load it into the converter.
| Description | Kilojoule (kJ) | Kilocalorie (Food Calorie) (kcal) | Kilowatt-hour (kWh) |
|---|---|---|---|
| 1 Kilojoule (1,000 Joules) | 1 | 0.23901 | 0.00027777 |
| 1 Dietary food Calorie (1 kcal) | 4.184 | 1 | 0.00116222 |
| 100 Kilojoules benchmark | 100 | 23.90057 | 0.02778 |
| Medium apple (~400 kJ / 95 kcal) | 400 | 95.60229 | 0.11111 |
| 1 Kilowatt-hour electricity (3,600 kJ) | 3,600 | 860.42065 | 1 |
| Daily adult diet (8,400 kJ / 2,000 kcal) | 8,368 | 2,000 | 2.32444 |
Energy Conversion Formulas
Use the following formulas to convert between kilojoules, kilocalories, and kilowatt-hours.
1 thermochemical kilocalorie (dietary Calorie) equals exactly 4.184 kilojoules (4,184 Joules).
More Kilojoule & Kilocalorie Conversions
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Frequently Asked Questions
All Energy Conversion Calculators (16)
Select any dedicated energy pair below for worked examples and printable tables
Category Conversion Matrix
Simultaneous comparison of 30 units in this category
Energy Unit Definitions & Symbols
Joule (J)
SICoherent SI unit of energy and work (1 W·s = 1 N·m).
Kilojoule (kJ)
METRICEqual to 1,000 Joules.
Megajoule (MJ)
SIEqual to 1,000,000 Joules.
Gigajoule (GJ)
SIEqual to 1,000,000,000 Joules, common in natural gas billing.
Millijoule (mJ)
METRICOne-thousandth of a Joule.
Microjoule (µJ)
METRICOne-millionth of a Joule.
Nanojoule (nJ)
METRICOne-billionth of a Joule.
Attojoule (aJ)
METRIC10⁻¹⁸ Joules.
Gram Calorie (cal) (cal)
OTHERThermochemical gram calorie defined as 4.184 Joules.
Kilocalorie (Food Calorie) (kcal)
OTHERDietary Calorie equal to 1,000 small calories (4,184 Joules).
Watt-hour (Wh)
METRICEqual to 3,600 Joules.
Kilowatt-hour (kWh)
METRICEqual to 3.6 Megajoules (1,000 Wh).
Megawatt-hour (MWh)
METRICEqual to 1,000 kilowatt-hours (3.6 Gigajoules).
Gigawatt-hour (GWh)
METRICEqual to 1,000 megawatt-hours (1,000,000 kWh).
British Thermal Unit (BTU) (BTU)
IMPERIALThermal energy unit equal to 1,055.056 Joules.
Million BTU (MMBTU) (MMBTU)
US CUSTOMARYEqual to 1,000,000 BTU (10 Therms ≈ 1.055 GJ).
Therm (US) (thm)
US CUSTOMARYNatural gas billing unit equal to 100,000 BTU (approx. 29.307 kWh).
Foot-pound (ft·lbf) (ft·lbf)
IMPERIALMechanical work unit equal to 1.355818 Joules.
Inch-pound (in·lbf) (in·lbf)
IMPERIAL1/12 of a foot-pound (0.112985 Joules).
Inch-ounce (in·ozf) (in·ozf)
IMPERIAL1/16 of an inch-pound (0.0070616 Joules).
Horsepower-hour (hp·h)
IMPERIALEnergy produced by 1 mechanical horsepower over 1 hour (0.7457 kWh).
Kilogram-force Meter (kgf·m) (kgf·m)
METRICWork done by 1 kgf over 1 meter (9.80665 Joules).
Electronvolt (eV)
SIAtomic energy unit equal to 1.602176634×10⁻¹⁹ Joules.
Kiloelectronvolt (keV)
SIEqual to 1,000 electronvolts.
Megaelectronvolt (MeV)
SIEqual to 1,000,000 electronvolts.
Erg (erg)
METRICCGS energy unit equal to 10⁻⁷ Joules.
Hartree Energy (Eₕ)
OTHERAtomic unit of energy (approx. 27.2114 eV).
Ton of TNT (t TNT)
OTHERDefined as 1 gigacalorie (4.184×10⁹ Joules).
Kiloton of TNT (kt TNT)
OTHEREqual to 1,000 tons of TNT (4.184×10¹² Joules).
Megaton of TNT (Mt TNT)
OTHEREqual to 1,000,000 tons of TNT (4.184×10¹⁵ Joules).
References
- [1]NIST CODATA StandardNIST CODATA (CODATA Energy & Thermodynamic Constants)·Energy Metrology Standards — Joule (J), Kilojoule (kJ) & Megajoule (MJ)
- [2]NIST SP 811 ReferenceNIST SP 811 (NIST SP 811 App. B.9 (Energy, Work & Heat))·International Reference Specification for Energy, Work & Heat
- [3]BIPM TablesBIPM (Derived SI Unit: Joule (J))·Official Energy Conversion Factors & Rounding Rules