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
Every energy unit is defined by an exact factor relative to the joule (the base unit). The calculator first turns the value you type into joules, then turns that into the unit you picked in the “To” menu and into each of the common units below it. This two-step method means any unit can be converted to any other – 15 units are available in each menu – and you can type into any field, including a result, to work in the other direction. Changing a unit menu keeps the quantity the same and just re-expresses it, and the page heading and copied results follow your choice.
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 |
What is a kilowatt-hour?
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.
What is a joule?
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.
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 J1 kWh = 3,600 kJ1 kWh = 3.6 MJ1 kWh = 860.42065 kcal1 kWh = 860,420.65 calWorked 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 do I change the units?
Pick any unit in the From and To menus. The value is converted in place, and the heading changes to show your conversion, for example “Kilowatt-hours to Joules Converter”.
Can I type into any field?
Yes. Every field is editable, so you can start from whichever unit you have.
How many units can I convert between?
15 energy units, from the everyday to the specialised.
Which units are exact?
All factors here are exact by definition except astronomical and similar reference values, which use internationally agreed constants.
What formula does the Energy Converter use?
1 kWh = 3,600,000 J.