Energy Converter
Electricity, food, gas, fuel and physics energy units — exact, in one table.
Type an energy in plain words — “500 kcal to kJ”, “3 kWh in MJ”, “1 MMBtu to kWh”, “2 kW for 3 h” — or use the boxes below.
Exact · MJ = kWh × 3.6
- Kilowatt-hour: 1 kW for one hour = 3.6 MJ exactly; the “unit” of electricity bills
- Megajoule: 1 MJ = 1,000,000 J
Energy from power and time
How much energy a device uses: its power × how long it runs. Take the power from the rating label; anything that switches itself on and off (a fridge, a heater with a thermostat) uses less than its rating on average.
The running time is then per day.
Type a power and a running time.
1 kWh in every unit
Select a unit to convert to it. Values marked ≈ are rounded; all others are exact.
| Unit | Value | Copy |
|---|---|---|
| SI (joules) | ||
| 3,60,00,00,000 | ||
| 36,00,000 | ||
| 3,600 | ||
| to | 3.6 | |
| 0.0036 | ||
| 0.0000036 | ||
| Electricity (watt-hours) | ||
| 10,00,000 | ||
| 1,000 | ||
| from | 1 | |
| 0.001 | ||
| 0.000001 | ||
| 1 × 10⁻⁹ | ||
| Calories | ||
| ≈ 8,60,420.6501 | ||
| ≈ 8,59,845.2279 | ||
| ≈ 860.4206501 | ||
| ≈ 859.8452279 | ||
| Heating & gas (Btu, therm) | ||
| ≈ 3,412.141633 | ||
| ≈ 0.0341212822 | ||
| ≈ 0.03412956341 | ||
| ≈ 0.003412141633 | ||
| ≈ 3.412141633 × 10⁻¹² | ||
| Energy statistics & explosives | ||
| ≈ 0.00008598452279 | ||
| ≈ 8.598452279 × 10⁻¹¹ | ||
| ≈ 0.0001228350326 | ||
| ≈ 0.0008604206501 | ||
| Mechanical | ||
| ≈ 26,55,223.737 | ||
| ≈ 1.34102209 | ||
| Physics | ||
| 3,60,00,00,00,00,000 | ||
| ≈ 2.246943267 × 10²⁵ | ||
| ≈ 2.246943267 × 10²² | ||
| ≈ 2.246943267 × 10¹⁹ | ||
Convert a list of values
Up to 1,000 lines. Fractions (3/4), mixed numbers (1 1/2) and grouped digits (1,250) are fine.
| Value | Result |
|---|
Quick reference
One of each unit in the units people compare most. Values marked ≈ are rounded to 6 significant digits.
| Energy | kJ | kWh | kcal | Btu |
|---|---|---|---|---|
| 1 kWh | 3,600 | 1 | ≈ 860.421 | ≈ 3,412.14 |
| 1 MJ | 1,000 | ≈ 0.277778 | ≈ 239.006 | ≈ 947.817 |
| 1 kcal | 4.184 | ≈ 0.00116222 | 1 | ≈ 3.96567 |
| 1,000 Btu | ≈ 1,055.06 | ≈ 0.293071 | ≈ 252.164 | 1,000 |
| 1 thm (US) | 105,480.4 | ≈ 29.3001 | ≈ 25,210.4 | ≈ 99,976.1 |
| 1 thm (EC) | 105,506 | ≈ 29.3072 | ≈ 25,216.5 | ≈ 100,000 |
| 1 MMBtu | ≈ 1,055,060 | ≈ 293.071 | ≈ 252,164 | 1,000,000 |
| 1 toe | 41,868,000 | 11,630 | ≈ 10,006,700 | ≈ 39,683,200 |
About the Energy Converter
Convert energy between joules (J, kJ, MJ, GJ, TJ), watt-hours (Wh, kWh — the “unit” of electricity bills — MWh, GWh, TWh), calories (the thermochemical and International Table calorie, the food kilocalorie), Btu, the US and EC therms, MMBtu and the quad, the energy-statistics units toe, Mtoe and tce, the ton of TNT, foot-pounds, the horsepower-hour, ergs and electronvolts. Type in either box and the other updates; the table underneath gives the value in every unit at once.
Every unit is stored as its exact definition — 1 kWh is exactly 3.6 MJ, the International Table Btu exactly 1,055.05585262 J, the food kilocalorie exactly 4.184 kJ — and the arithmetic uses exact fractions, so a result is rounded only when it is shown (and then marked ≈). To find how much energy a device uses, enter its power and running time under Energy from power and time, or type 1500 W for 3 h in Quick convert.
How to use it
- Type a number in From and pick its unit, then pick the unit you want in To — or type
500 kcal to kJin Quick convert and press Enter. - Read the result and the formula under it; the table below shows the same energy in every unit. Select a unit name in the table to convert to it.
- For an appliance, fill in Energy from power and time: its power (on the rating label), how long it runs and, optionally, on how many days. Press Show in the converter to see that energy in every unit.
- Copy the result or a link, download the table as CSV, or open Convert a list of values for a column of readings.
Examples
250 kWh to MJ
900 MJ
1 kWh is exactly 3.6 MJ: one kilowatt for one hour.
500 kcal to kJ
2,092 kJ
A food Calorie (Cal) is a kilocalorie, 4.184 kJ.
40 therm US to kWh
≈ 1,172 kWh
The US therm is exactly 105,480,400 J ≈ 29.3 kWh.
1 MMBtu to kWh
≈ 293.07 kWh
A million Btu is about 1.055 GJ.
1500 W for 3 h
4.5 kWh = 16.2 MJ
Energy = power × time.
1 eV to J
1.602176634 × 10⁻¹⁹ J
Exact, because the elementary charge is fixed in the SI.
Common uses
- Electricity: compare kWh on a bill or a battery with MJ, Btu or kcal, and estimate what an appliance uses.
- Gas and heating: therms, kWh, MJ and MMBtu on bills, boiler data and gas price quotes.
- Food and exercise: kilocalories and kilojoules on labels and fitness trackers.
- Energy statistics: tonnes of oil or coal equivalent against TWh, PJ and quads.
- Physics and chemistry homework: joules, ergs, electronvolts and calories with exact factors.
Which calorie, Btu and therm this page uses
- Calorie (cal) is the thermochemical calorie, exactly 4.184 J, and the kilocalorie (kcal) is 1,000 of them, 4.184 kJ — the “Calories” printed on food labels. The International Table calorie (4.1868 J) of steam tables and energy statistics is 0.07 % larger; it is listed separately as cal (IT) and kcal (IT).
- Btu is the International Table British thermal unit, exactly 1,055.05585262 J. MMBtu is a million of them (natural gas is priced per MMBtu) and a quad 10¹⁵ of them.
- The US therm is exactly 105,480,400 J, the legal unit of the US natural gas industry; the EC therm is exactly 105,506,000 J. Both are about 100,000 Btu and they differ by 0.024 %, so pick the one your bill or contract uses. A dekatherm (Dth) is 10 therms, which US gas trade counts as 1 MMBtu; because those two also differ by 0.024 %, type
10 therm USor1 MMBtufor it. - toe (tonne of oil equivalent) is 41.868 GJ and tce (tonne of coal equivalent) 0.7 toe, by the convention of the IEA. They are units of energy statistics, not the energy of a particular tonne of fuel.
Energy, power and time
Energy is power multiplied by time. One kilowatt running for one hour uses one kilowatt-hour, so a 1,500 W heater on for 3 hours uses 4.5 kWh, and 8 hours a day for 30 days is 360 kWh. A device’s label gives its rated (maximum) power; anything that switches itself on and off — a fridge, an air conditioner, a heater with a thermostat — uses less than its rating on average, so the panel gives an upper estimate. To convert the power itself (W, kW, hp, Btu/h, tons of refrigeration), use the Power Converter.
A newton metre of work is a joule, but N·m is also the unit of torque, a different quantity; the SI never expresses torque in joules. Torque has its own Torque Unit Converter.
Where the factors come from
- NIST SP 811, Appendix B: the thermochemical and International Table calories, the kilowatt-hour, both therms, the erg and the ton of TNT (exact), and the International Table Btu, exactly 1.05505585262 kJ (footnotes).
- The SI Brochure, Table 8: 1 eV = 1.602176634 × 10⁻¹⁹ J exactly.
- The IEA Energy Statistics Manual: 1 toe = 41.868 GJ and 1 tce = 7 million kcal = 0.7 toe.
- The foot-pound and horsepower-hour follow from the exact pound (0.45359237 kg), foot (0.3048 m) and standard gravity (9.80665 m/s²).
Limitations
- Fuels are not converted by volume or mass here — a litre of diesel or a cubic metre of gas holds an amount of energy that depends on the fuel. For gas meter readings use Gas Units to kWh.
- The power-and-time estimate assumes the device runs at the power you enter the whole time.
- toe, Mtoe and tce are statistical conventions; the energy in real oil or coal varies from one cargo to the next.
- Results are exact fractions shown to 10 significant digits (marked ≈ when rounded); very large and very small values use scientific notation.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How many joules are in a kilowatt-hour?
Exactly 3,600,000 J (3.6 MJ): one kilowatt is 1,000 joules per second, and an hour has 3,600 seconds.
How many Btu are in a kWh?
About 3,412.14 Btu. One International Table Btu is exactly 1,055.05585262 J, and 3,600,000 ÷ 1,055.05585262 ≈ 3,412.14.
What is the difference between cal, kcal and Calories?
A small calorie (cal) is 4.184 J. A kilocalorie (kcal) is 1,000 of them, 4.184 kJ — and that is what food labels mean by Calories (Cal). Type Cal with a capital C in Quick convert for food Calories.
Which therm should I use?
US gas bills use the US therm (105,480,400 J ≈ 29.30 kWh). The EC therm (105,506,000 J ≈ 29.31 kWh) is the European definition. They differ by 0.024 %, which matters only on large contracts.
How do I work out how many kWh an appliance uses?
Multiply its power in kilowatts by the hours it runs: a 2,000 W (2 kW) heater on for 3 hours uses 6 kWh. Use Energy from power and time on this page, or type 2 kW for 3 h in Quick convert.
Is a newton metre the same as a joule?
For work and energy, yes: 1 N·m = 1 J. But N·m is also the unit of torque, which is not energy, and the SI never writes torque in joules. Use the Torque Unit Converter for torque.
What is a tonne of oil equivalent?
A unit of energy statistics: 41.868 GJ (10 million International Table kilocalories) by the convention of the IEA and Eurostat, about 11.63 MWh or 39.68 MMBtu.