Kcal to kJ Converter
Convert kilocalories to kilojoules — the two numbers on every food label. Results update as you type; exact factors shown.
One kilocalorie (food Calorie) is 4.184 kilojoules — see the exact factor, not a rounded rule of thumb.
How the kcal to kj converter works
Energy converts through the joule. A thermochemical calorie is exactly 4.184 J, so a food Calorie (kcal) is 4.184 kJ. A kilowatt-hour is exactly 3.6 MJ. A BTU is 1,055.056 J and a US therm is 100,000 BTU.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common energy conversions
| From | To | Units |
|---|---|---|
| 50 kcal | 209.2 kJ | kilocalorie (food Calorie) to kilojoules |
| 100 kcal | 418.4 kJ | kilocalorie (food Calorie) to kilojoules |
| 150 kcal | 627.6 kJ | kilocalorie (food Calorie) to kilojoules |
| 200 kcal | 836.8 kJ | kilocalorie (food Calorie) to kilojoules |
| 250 kcal | 1,046 kJ | kilocalorie (food Calorie) to kilojoules |
| 300 kcal | 1,255.2 kJ | kilocalorie (food Calorie) to kilojoules |
| 500 kcal | 2,092 kJ | kilocalorie (food Calorie) to kilojoules |
| 1,000 kcal | 4,184 kJ | kilocalorie (food Calorie) to kilojoules |
| 1,500 kcal | 6,276 kJ | kilocalorie (food Calorie) to kilojoules |
| 2,000 kcal | 8,368 kJ | kilocalorie (food Calorie) to kilojoules |
| 2,500 kcal | 10,460 kJ | kilocalorie (food Calorie) to kilojoules |
| 3,000 kcal | 12,552 kJ | kilocalorie (food Calorie) to kilojoules |
Units in this converter and their exact factors
| Unit | Symbol | One unit in joules |
|---|---|---|
| joule | J | 1 joule |
| kilojoule | kJ | 1,000 joule |
| megajoule | MJ | 1,000,000 joule |
| calorie (thermochemical) | cal | 4.184 joule |
| kilocalorie (food Calorie) | kcal | 4,184 joule |
| watt-hour | Wh | 3,600 joule |
| kilowatt-hour | kWh | 3,600,000 joule |
| British thermal unit | BTU | 1,055.05585262 joule |
| therm (US) | thm | 105,505,585.262 joule |
| foot-pound | ft·lb | 1.3558179483 joule |
FAQFrequently asked questions about energy conversion
How many kJ in a kcal?
4.184.
Is a kcal the same as a food Calorie?
Yes — a capital-C Calorie on a label is a kilocalorie.
What is a 2,000 kcal diet in kJ?
8,368 kJ.
Why do labels show both?
Because kilojoules are the SI unit while kilocalories are what most people know.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.