Calories to Kilojoules Converter
Convert food Calories to kilojoules — one Calorie is 4.184 kJ. 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 calories to kilojoules 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 US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
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 |
| 200 kcal | 836.8 kJ | kilocalorie (food Calorie) to kilojoules |
| 250 kcal | 1,046 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 |
| 4,000 kcal | 16,736 kJ | kilocalorie (food Calorie) to kilojoules |
| 5,000 kcal | 20,920 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 kilojoules in a Calorie?
4.184 kJ for the food Calorie, which is really a kilocalorie.
What is 2,000 Calories in kJ?
8,368 kJ — close to the 8,700 kJ Australian daily reference.
Why is Calorie capitalised?
Because the food Calorie is 1,000 small calories. The capital is meant to distinguish them, though almost nobody observes it.
Which do labels use?
Kilojoules in Australia and New Zealand by law; Calories in the US; both in the UK and EU.
How do I convert quickly?
Multiply Calories by 4.2 for a close estimate.
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 Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.