kcal to kJ Converter
Type kilocalories, the “Calories” on a food label, to get kilojoules. 2,000 kcal is 8,368 kJ.
2,000 kcal =
8,368kJ
2,000 kilocalories is 8,368 kilojoules.
- 1 kcal
- 4.184 kJ
- 1 kJ
- 0.239 kcal
How this works: Method, 5 sources,
How this works
Method
Multiply kilocalories by 4.184. The “Calories” on a food label are kilocalories, and the calorie used for food energy is the thermochemical calorie of exactly 4.184 joules, so one kilocalorie is exactly 4.184 kilojoules. Full method
Sources
- FAO Food and Nutrition Paper 77, Food energy: methods of analysis and conversion factors
- EU Regulation 1169/2011 on food information to consumers
- NIST SP 811, Appendix B.8: conversion factors by unit
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement
- BIPM, The International System of Units (SI Brochure, 9th edition)
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Changes
- Ask understands “5 ft 9 in to cm” and “2 cups of flour in grams” and answers at once, and a decimal comma (“2,5”) reads as 2.5.
- First published: 89 everyday units across ten quantities, with 58 pages for common pairs such as cm to inches and Celsius to Fahrenheit.
How to convert kcal to kJ
Multiply kilocalories by 4.184. The “Calories” on a food label are kilocalories, and the calorie used for food energy is the thermochemical calorie of exactly 4.184 joules, so one kilocalorie is exactly 4.184 kilojoules.
For a 250 kcal snack bar: 250 × 4.184 = 1,046 kJ. An Australian or European pack of the same bar would print about 1,046 kJ (often rounded to 1,050) beside or instead of the kcal figure.
Labels can disagree by a percent or so because they are not converted from each other. EU rules give each nutrient its own pair of factors (fat 37 kJ or 9 kcal per gram, protein and carbohydrate 17 kJ or 4 kcal), and 9 × 4.184 is 37.66, not 37.
kilojoules = kilocalories × 4.184
- FAO recommends expressing food energy in joules and converting with 1 kcal = 4.184 kJ. Source: FAO Food and Nutrition Paper 77, Food energy: methods of analysis and conversion factors.
- EU nutrition declarations must state energy in both kJ and kcal, using fixed factors per gram of fat, carbohydrate, protein and alcohol. Source: EU Regulation 1169/2011 on food information to consumers.
How to estimate kcal to kJ in your head
Multiply by 4, then add 5%. 500 kcal × 4 = 2,000, plus 100 is 2,100, against an exact 2,092 kJ. Times 4 alone is about 4.4% low, so it works when you only need a rough sense of a label.
kcal to kJ chart
From a gram of each macronutrient to a full day’s intake.
| Kilocalories (kcal) | Kilojoules (kJ) | Example |
|---|---|---|
| 1 | 4.184 | |
| 4 | 16.736 | a gram of protein or carbohydrate |
| 7 | 29.288 | a gram of alcohol |
| 9 | 37.656 | a gram of fat |
| 50 | 209.2 | |
| 100 | 418.4 | |
| 150 | 627.6 | |
| 200 | 836.8 | |
| 250 | 1,046 | |
| 300 | 1,255.2 |
Show all 20 rowsShow fewer
| 400 | 1,673.6 | |
| 500 | 2,092 | |
| 600 | 2,510.4 | |
| 800 | 3,347.2 | |
| 1,200 | 5,020.8 | |
| 1,500 | 6,276 | |
| 1,800 | 7,531.2 | |
| 2,000 | 8,368 | the reference adult intake on labels |
| 2,500 | 10,460 | |
| 3,000 | 12,552 |
Frequently Asked Questions
How many kJ is 2,000 calories?
2,000 kcal is 8,368 kJ at 4.184 kJ per kcal. EU labels use a reference intake of 8,400 kJ / 2,000 kcal, a rounded pairing rather than an exact conversion.
Are Calories and kcal the same?
Yes. A food Calorie, often written with a capital C, is one kilocalorie: 1,000 small calories. So “250 Calories” and “250 kcal” mean the same energy, 1,046 kJ.
Why does my label’s kJ figure not match kcal × 4.184?
Manufacturers work out kJ and kcal separately from the nutrients, with rounded factors such as 17 kJ and 4 kcal per gram of carbohydrate (4 × 4.184 would be 16.7). The two figures land close but rarely on the exact ratio.