Your electricity bill counts kilowatt-hours, a food label counts kilocalories, a gas bill counts therms and a physics textbook counts joules or electronvolts. All of them measure the same thing, energy, and the joule ties them together.
How to use the Energy Converter
- Pick the unit you are starting from in the From menu and type your value.
- Pick the unit you want in the To menu. The heading changes to match, for example “Kilowatt-hours to Joules Converter”.
- The most common energy units are shown below at the same time, so you can compare them at a glance.
- Type into any result to convert backwards, then use Copy results. The copied text starts with the heading for your chosen units.
Results update as you type. Everything is calculated in your browser.
How it works
Each of the 15 energy units on this page is defined by an exact factor relative to the joule, the base unit: 1 kWh = 3,600,000 J and 1 kJ = 1,000 J, for example. The calculator first turns the value you type into joules, then turns that into the unit you picked in the “To” menu and into kilojoules, megajoules and kilocalories. Typing into any result works backwards the same way, so the kilowatt-hours and joules values always describe the same amount.
How to convert energy units
- Choose the unit you have in the From menu and type the value, for example 1 kWh.
- Choose the unit you want in the To menu, for example joules. The page heading changes to “Kilowatt-hours to Joules Converter”.
- The calculator multiplies by the joule factor of the “from” unit and divides by the factor of the “to” unit: 1 kWh × 3,600,000 ÷ 1 = 3,600,000 J.
1 kilowatt-hour in common units
| Unit | Value |
|---|---|
| Joules (J) | 3,600,000 |
| Kilojoules (kJ) | 3,600 |
| Megajoules (MJ) | 3.6 |
| Kilocalories (kcal) | 860.42065 |
| Calories (cal) | 860,420.65 |
| Watt-hours (Wh) | 1,000 |
| British thermal units (BTU) | 3,412.1416 |
| Therms (therm) | 0.034121416 |
| Electronvolts (eV) | 2.246943 × 1025 |
Kilowatt-hours conversion table
| Kilowatt-hours | J | kJ | MJ | kcal |
|---|---|---|---|---|
| 0.001 | 3,600 | 3.6 | 0.0036 | 0.86042065 |
| 0.1 | 360,000 | 360 | 0.36 | 86.042065 |
| 1 | 3,600,000 | 3,600 | 3.6 | 860.42065 |
| 10 | 36,000,000 | 36,000 | 36 | 8,604.2065 |
| 100 | 360,000,000 | 360,000 | 360 | 86,042.065 |
| 1,000 | 3.6 × 109 | 3,600,000 | 3,600 | 860,420.65 |
Energy units explained
- Kilowatt-hour (kWh)
- A kilowatt-hour is the energy used by a 1 kW appliance running for one hour, 3.6 million joules. Electricity bills are charged per kWh.
- Joule (J)
- The joule is the SI unit of energy: the work done by a force of one newton over one metre. It is also one watt for one second.
- Kilocalorie (kcal)
- A kilocalorie (a food Calorie) is the energy needed to warm one kilogram of water by about 1 °C, 4,184 J. Food labels use kcal or Calories.
- British thermal unit (BTU)
- The British thermal unit is the energy to warm one pound of water by 1 °F, about 1,055 J. Furnaces, air conditioners and gas appliances are rated in BTU or BTU per hour.
- Therm (therm)
- A therm is 100,000 BTU, about 29.3 kWh. U.S. natural gas is billed in therms.
Common mistakes to avoid
Confusing energy (kWh, J) with power (kW, W), and food Calories (kcal) with small calories (cal).
Formula
1 kWh = 3,600,000 J
1 kWh = 3,600 kJ
1 kWh = 3.6 MJ
1 kWh = 860.42065 kcal
1 kWh = 860,420.65 cal
Worked example
Inputs: From: 1 kWh.
Results: To = 3,600,000 J; Kilojoules = 3,600 kJ; Megajoules = 3.6 MJ; Kilocalories = 860.4206501 kcal; Calories = 860,420.6500956 cal; Watt-hours = 1,000 Wh; British thermal units = 3,412.14163313 BTU.
Frequently asked questions
How many kcal in a kWh?
About 860.4 kcal.
Is a food Calorie the same as a calorie?
No. A food Calorie (capital C) is a kilocalorie, 1,000 small calories.
How many joules in a BTU?
About 1,055.06 J.
How many joules are in one kilowatt-hour?
1 kWh = 3,600,000 J.
How many kilojoules are in one kilowatt-hour?
1 kWh = 3,600 kJ.
How many megajoules are in one kilowatt-hour?
1 kWh = 3.6 MJ.
Are these energy conversions exact?
Yes. Every factor is an exact definition (for example 1 kWh = 3,600,000 J), so any difference you see is rounding in the last displayed digit.