Energy
Calories to kilojoules converter
Food "calories" are kilocalories, and 1 kcal = 4.184 kJ. UK food labels show energy in both units; convert either way below.
Calories to kilojoules converter
250 kcal = 1,046 kJ
How to convert
kJ = kcal × 4.184
kcal = kJ ÷ 4.184
Multiply kcal by 4 and add a little under 5% for kJ; divide kJ by about 4.2 for kcal.
Worked examples
- A 250 kcal snack: 250 × 4.184 = 1,046 kJ
- The adult reference intake of 2,000 kcal: 2,000 × 4.184 = 8,368 kJ
- A meal labelled 1,500 kJ: 1,500 ÷ 4.184 ≈ 358.5 kcal
"=" means the result is exact; "≈" means it has been rounded for display.
Calories to kilojoules converter table
| Kilocalories (kcal) | Kilojoules (kJ) |
|---|---|
| 1 | ≈ 4.2 |
| 50 | 209.2 |
| 100 | 418.4 |
| 150 | 627.6 |
| 200 | 836.8 |
| 250 | 1,046 |
| 300 | 1,255.2 |
| 500 | 2,092 |
| 1,000 | 4,184 |
| 1,500 | 6,276 |
| 2,000 | 8,368 |
| 2,500 | 10,460 |
Values marked ≈ are rounded; all others are exact.
Calories, kilocalories and Calories
Strictly, a calorie (cal) is a tiny unit of energy, and food energy is measured in kilocalories (kcal), each 1,000 calories. In everyday speech, and on some American labels, "calories" or "Calories" means kilocalories. The conversion 1 kcal = 4.184 kJ uses the thermochemical calorie, the value used for food labelling.
Reading UK labels
UK and EU nutrition labels give energy per 100 g or 100 ml in kJ and kcal, and front-of-pack labels often show a percentage of the adult reference intake, which is 8,400 kJ or 2,000 kcal per day. Note that 2,000 × 4.184 = 8,368 kJ; the reference figure is rounded to 8,400.
Frequently asked questions
How many kJ in 100 kcal?
418.4 kJ.
How many kcal is 1,000 kJ?
1,000 ÷ 4.184 ≈ 239 kcal.
Is a food Calorie the same as a kcal?
Yes. A food Calorie with a capital C is one kilocalorie.