Energy Converter
Convert between joules, kilojoules, calories, kilocalories (the food Calorie), watt-hours, kilowatt-hours (the electricity unit on your bill) and British thermal units. One food Calorie is 1 kcal = 4.184 kJ, and one kWh is exactly 3.6 megajoules.
1 kilocalorie (food calorie) = 4.184 kilojoules. Formula: kJ = kcal × 4.184 (or kcal ÷ 0.23900574)
1 kilocalorie (food calorie) in all energy units
| Joules (J) | 4,184 |
| Kilojoules (kJ) | 4.184 |
| Calories (cal) | 1,000 |
| Watt-hours (Wh) | 1.1622222 |
| Kilowatt-hours (kWh) | 0.0011622222 |
| BTU (BTU) | 3.9656668 |
Energy units on this page
| Unit | Symbol | 1 unit equals |
|---|---|---|
| Joule | J | 1 J |
| Kilojoule | kJ | 1,000 J |
| Calorie (small) | cal | 4.184 J |
| Kilocalorie (food Calorie) | kcal | 4,184 J |
| Watt-hour | Wh | 3,600 J |
| Kilowatt-hour (unit) | kWh | 3,600,000 J |
| British thermal unit | BTU | 1,055.0559 J |
To convert, the value is first expressed in the base unit and then divided by the factor of the target unit, so any pair of units on this page can be converted in one step.
Common energy conversions
| From | To |
|---|---|
| 1 kilocalorie (food calorie) | 4.184 kJ |
| 1 kilojoule | 0.23900574 kcal |
| 1 kilowatt-hour (unit) | 3,600 kJ |
| 1 british thermal unit | 1.0550559 kJ |
| 2,000 kilocalories | 8,368 kJ |
| 1 kilowatt-hour (unit) | 860.42065 kcal |
| 1 kilowatt-hour (unit) | 3,412.1416 BTU |
| 1 calorie (small) | 4.184 J |
Food labels and electricity bills
Nutrition labels in the US list Calories (kcal); in Australia, New Zealand and much of Europe they list kilojoules, sometimes alongside kcal. Multiply kcal by 4.184 to get kJ. A 2,000 kcal daily intake is 8,368 kJ. Electricity is billed per kilowatt-hour, called a unit in India and the UK. One kWh is 3,600 kJ or 860 kcal, enough to run a 10 W LED bulb for 100 hours. Air conditioner and heater capacities are still quoted in BTU per hour in some countries: 12,000 BTU/h is 3.517 kW, which is one ton of refrigeration.
Frequently asked questions
How many kJ are in a calorie?
A food Calorie (kcal) is 4.184 kJ. A small calorie (cal), used in chemistry, is 4.184 J. Food labels always mean kcal even when they print Calories or cal.
How many kcal are in a kWh?
860.42 kcal. One kilowatt-hour is 3,600 kJ, and 3,600 ÷ 4.184 = 860.42.
What is a unit of electricity?
One kilowatt-hour: a 1,000 W appliance running for one hour, or a 100 W device for 10 hours. Bills in India and the UK price electricity per unit.
How many BTU are in a kWh?
3,412.14 BTU. Air conditioners rated in BTU per hour can be converted to kilowatts by dividing by 3,412.
Related calculators
Last updated . Formulas are shown on the page and checked against the worked example.
Conversion factors are exact international definitions where one exists and standard reference values elsewhere. Results are rounded to 8 significant digits.