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Converters & physics calculator

Energy unit converter: J, kWh, BTU, therm, calorie, toe and 30+ units

Convert any amount of energy between joules, watt-hours, calories, BTU, therms, tonnes of oil or coal equivalent, barrels of oil equivalent, electronvolts and foot-pounds. Shows all units at once, with real-world equivalents.

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Results

1 kWh = 3.6 MJ · 1 MJ = 0.2777778 kWh
1 kilowatt-hour (kWh) in MJ
3.6MJ
Kilowatt-hours
1kWh
Megajoules
3.6MJ
BTU
3,412BTU
Kilocalories
859.8kcal
Oil equivalent
0.08598kg oe
Runs a 10 W LED for
4.167 days
Drives an EV about
5.882km
at 17 kWh/100 km
Petrol with same energy
0.1091litres
LHV 9.17 kWh/L

SI units

Unit1 kWh equals1 unit in kWh
joule (J)3,600,0002.777778 × 10⁻⁷
kilojoule (kJ)3,6000.0002777778
megajoule (MJ)3.60.2777778
gigajoule (GJ)0.0036277.7778
terajoule (TJ)0.0000036277,778
petajoule (PJ)3.6 × 10⁻⁹277,777,778
exajoule (EJ)3.6 × 10⁻¹²277,777,777,778

Electrical units

Unit1 kWh equals1 unit in kWh
watt-hour (Wh)1,0000.001
kilowatt-hour (kWh)11
megawatt-hour (MWh)0.0011,000
gigawatt-hour (GWh)0.0000011,000,000
terawatt-hour (TWh)1 × 10⁻⁹1,000,000,000

Heat units

Unit1 kWh equals1 unit in kWh
calorie (cal, IT)859,8450.000001163
kilocalorie (kcal, food Calorie)859.84520.001163
megacalorie / thermie (Mcal)0.85984521.163
gigacalorie (Gcal)0.00085984521,163
British thermal unit (BTU, IT)3,412.1420.0002930711
thousand BTU (kBtu, MBtu)3.4121420.2930711
therm (100,000 BTU)0.0341214229.30711
million BTU (MMBtu)0.003412142293.0711
quad (10¹⁵ BTU)3.412142 × 10⁻¹²293,071,070,172

Fuel equivalents units

Unit1 kWh equals1 unit in kWh
tonne of oil equivalent (toe)0.0000859845211,630
thousand toe (ktoe)8.598452 × 10⁻⁸11,630,000
million toe (Mtoe)8.598452 × 10⁻¹¹11,630,000,000
barrel of oil equivalent (boe)0.00058844071,699.406
tonne of coal equivalent (tce)0.0001228358,141
cubic metre natural gas (≈ 10.55 kWh gross)0.0947368410.55556

Physics units

Unit1 kWh equals1 unit in kWh
electronvolt (eV)2.246943 × 10²⁵4.450491 × 10⁻²⁶
megaelectronvolt (MeV)2.246943 × 10¹⁹4.450491 × 10⁻²⁰
erg36,000,000,000,0002.777778 × 10⁻¹⁴

Mechanical units

Unit1 kWh equals1 unit in kWh
foot-pound force (ft·lbf)2,655,2243.766161 × 10⁻⁷
horsepower-hour (hp·h, mechanical)1.3410220.7456999
metric horsepower-hour (PS·h)1.3596220.7354988
  • Calorie = International Table calorie (4.1868 J); the thermochemical calorie (4.184 J) differs by 0.07%. BTU = International Table BTU.
  • toe = 41.868 GJ (IEA/OECD convention, 10 Gcal); tce = 29.3076 GJ (7 Gcal); boe = 5.8 MMBtu ≈ 6.118 GJ. These are accounting conventions, not physical constants.
  • The natural-gas cubic metre uses a typical gross calorific value of 38 MJ/m³. Real gas varies from 35 to 42 MJ/m³ depending on origin; see the gas unit converter.

How to use the energy unit converter

Type an amount, choose the unit it is in and the unit you want. The big tile gives the answer; underneath, every one of the 33 units is listed at once, grouped into SI, electrical, heat, fuel-equivalent, physics and mechanical units, together with the size of one of each unit expressed in your starting unit. Very large and very small numbers switch automatically to scientific notation, so the same tool handles a single electronvolt and the world’s annual energy use.

A row of everyday equivalents (hours of a 10 W LED, kilometres in an electric car, litres of petrol) makes abstract quantities easier to picture.

The formula

value_target = value_source × (joules per source unit) ÷ (joules per target unit)

1 Wh = 3,600 J 1 kWh = 3.6 MJ 1 cal(IT) = 4.1868 J 1 BTU(IT) = 1,055.056 J 1 therm = 10⁵ BTU 1 toe = 41.868 GJ 1 tce = 29.3076 GJ 1 eV = 1.602176634 × 10⁻¹⁹ J

All conversions pass through the joule, the SI unit of energy, so there is no rounding drift between unit pairs.

Worked example

The default converts 1 kWh to megajoules: 1 × 3,600,000 J ÷ 1,000,000 J = 3.6 MJ. The table shows the same kilowatt-hour as 3,412 BTU, 860 kcal, 0.034 therm, 0.086 kg of oil equivalent and 2.25 × 10²⁵ eV. It would run a 10 W LED bulb for about four days or move an efficient electric car roughly 6 km.

Quick reference table

From kWh MJ BTU kcal
1 kWh 1 3.6 3,412.1 859.8
1 MJ 0.2778 1 947.8 238.8
1 GJ 277.8 1,000 947,817 238,846
1 BTU 0.000293 0.001055 1 0.252
1 therm 29.307 105.51 100,000 25,200
1 MMBtu 293.07 1,055.1 1,000,000 251,996
1 kcal 0.001163 0.004187 3.968 1
1 Gcal 1,163 4,186.8 3,968,321 1,000,000
1 toe 11,630 41,868 39.68 million 10 million
1 boe 1,699.4 6,117.9 5.8 million 1.46 million
1 tce 8,141 29,308 27.78 million 7 million
1 ft·lbf 3.766 × 10⁻⁷ 1.356 × 10⁻⁶ 0.001285 0.000324

Large-scale energy units

Unit Equals Typical use
1 TWh 3.6 PJ = 86 ktoe National electricity statistics
1 Mtoe 11.63 TWh = 41.87 PJ IEA and Eurostat energy balances
1 EJ 277.8 TWh = 23.9 Mtoe Global energy (world ≈ 620 EJ/yr)
1 quad 1.055 EJ = 293 TWh US Energy Information Administration

Which unit for what?

  • kWh / MWh: electricity bills, batteries, EV charging, power plants. See the kWh cost calculator.
  • MJ / GJ: fuels, industry, scientific work; also district heating in some countries.
  • BTU, therm, MMBtu: gas and heating in the US and UK; gas trading at Henry Hub.
  • kcal / Gcal: food energy; district heating in Eastern Europe and Russia.
  • toe, boe, tce: energy statistics and oil & gas reserves; they are conventions, not physical properties of a specific fuel.
  • eV, MeV: atomic and nuclear physics (one U-235 fission releases about 200 MeV).

Tips and pitfalls

  1. Calorie variants. The International Table calorie (4.1868 J) is used here; the thermochemical calorie (4.184 J) differs by 0.07%. Food labels use kilocalories but often write “Calories”.
  2. Gross vs net. Fuel-equivalent units hide a heating-value convention: IEA toe is net (LHV), while gas therms are usually gross (HHV). Use the fuel energy content calculator when the fuel matters.
  3. Energy vs power. kW, hp and BTU/h are rates. To convert those, use the power unit converter.
  4. Cubic metres of gas vary between 35 and 42 MJ by origin and pressure conditions; the gas unit converter handles calorific value and correction factors.

Limitations

Fuel-equivalent units (toe, boe, tce, m³ of gas) are statistical conventions and differ slightly between organisations. BP and the Energy Institute, for instance, use 7.33 barrels per tonne of oil. All other factors are exact by definition or fixed by international standards.

Method & assumptions

Every unit is converted through joules: value in target unit = value × (joules per source unit) ÷ (joules per target unit). 1 Wh = 3,600 J exactly; 1 kWh = 3.6 MJ; 1 calIT = 4.1868 J; 1 BTUIT = 1,055.05585262 J; 1 therm = 100,000 BTU; 1 eV = 1.602176634 × 10−19 J (exact since the 2019 SI redefinition).

Frequently asked questions

How many MJ are in 1 kWh?
Exactly 3.6 MJ. One watt is one joule per second, so one kilowatt-hour = 1,000 J/s × 3,600 s = 3,600,000 J.
How many kWh is 1 therm?
One therm is 100,000 BTU = 105.5 MJ = 29.31 kWh. UK and US gas bills that quote therms can be converted to kWh by multiplying by 29.31.
How many kWh in a BTU, and BTU in a kWh?
1 kWh = 3,412.14 BTU, and 1 BTU = 0.000293 kWh (0.293 Wh). One million BTU (MMBtu), the unit of US gas prices, is 293.07 kWh.
How many kWh are in 1 calorie or kilocalorie?
One food Calorie (1 kcal) is 4,186.8 J = 0.001163 kWh. A 2,000 kcal daily diet therefore contains about 2.3 kWh of energy, roughly what a fridge uses in two days.
What is a tonne of oil equivalent (toe)?
An accounting unit used in energy statistics: by IEA/OECD convention 1 toe = 10 Gcal = 41.868 GJ = 11.63 MWh, roughly the net energy in a tonne of crude oil. A barrel of oil equivalent (boe) is about 6.12 GJ (5.8 MMBtu), and a tonne of coal equivalent (tce) is 29.31 GJ.
How do I convert TWh to EJ?
1 EJ = 277.8 TWh, and 1 TWh = 0.0036 EJ. World primary energy consumption of around 620 EJ a year is therefore about 172,000 TWh.

Sources & references

  1. BIPM: The International System of Units (SI Brochure, 9th edition, 2019)
  2. NIST Special Publication 811: Guide for the Use of the International System of Units (conversion factors)
  3. IEA: Unit converter and glossary (toe, energy balance conventions)
  4. Energy Institute: Statistical Review of World Energy: approximate conversion factors

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