Unit converter
Energy.
Convert kcal to kJ, or pick any of the 17 units in the menus. Type in either box and the other follows. Joules, calories, kilowatt-hours and BTU all measure the same quantity — and the calorie on a food label is a thousand of the calorie in a physics book.
| kcal | kJ |
|---|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 3 kcal | 12.552 kJ |
| 4 kcal | 16.736 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 15 kcal | 62.76 kJ |
| 20 kcal | 83.68 kJ |
| 25 kcal | 104.6 kJ |
| 50 kcal | 209.2 kJ |
| 75 kcal | 313.8 kJ |
| 100 kcal | 418.4 kJ |
| 250 kcal | 1046 kJ |
| 500 kcal | 2092 kJ |
| 1000 kcal | 4184 kJ |
- Every unit in the menus is defined against J, so any pairing converts by the same single route.
Definitions
- The kilocalorie is 1000 small calories. It is what food labels and fitness apps mean when they say "calories".
- The kilojoule is 1000 joules, and the energy unit on UK and EU nutrition labels alongside kilocalories.
- The food calorie is the kilocalorie: 1 kcal = 1000 cal. Nutrition labels marked "calories" mean kcal.
- 16 of the 17 units are exact by definition; the rest are conventional or measured values. The display says which kind you are looking at.
How it works
Every value is converted into joules and then back out into the unit you asked for. One route covers every pairing in the menus, so an unusual combination is no less accurate than a common one, and adding a unit affects only that unit.
Both boxes are live. Whichever one you last typed in is the source, changing either menu recalculates straight away, and Swap exchanges the units and the values so the number you are reading stays where you are looking.
Display precision limits significant figures rather than decimal places, because one fixed number of decimals is useless across a range this wide. Very large and very small results switch to scientific notation with a proper superscript exponent. The editable box always holds a plain number at full working precision, so you can carry on from either side.
Common questions this answers: how many kilojoules in a kilocalorie (food calorie) (4.184), how many kilocalories in a kilojoule (0.239006), and what 500 kcal is in kilojoules (2092 kJ).
Common conversions
- Food calories to kilojoules
- Kilojoules to food calories
- Joules to thermochemical calories
- Kilowatt-hours to megajoules
- All converters
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- No account
- Works offline once loaded
From the maker of Ans — a scientific calculator you can own. Same idea: a proper instrument, nothing in the way.