Quick answer
100 kcal = 418.4 kJ. Multiply 100 by 4.184 to check: 100 × 4.184 = 418.4.
How to convert 100 calories to kJ
- Start with 100 calories (kcal).
- Multiply by 4.184: 100 × 4.184 = 418.4 kJ.
- For joules, multiply by 4,184: that gives 418,400 J.
You may also see this searched as 100 cal to kj or 100 calories to kilojoules. A small calorie (cal) is different: 100 cal is 0.4184 kJ. Food labels almost always mean kcal. See the calories to kJ converter for more.
100 kcal in context
- 4.8% of the 8,700 kJ average-adult reference day on Australian and New Zealand labels.
- 5% of a 2,000 kcal reference day, as used on EU and US labels.
- Reference intakes are label conventions. Your own needs depend on age, sex, size and activity. See how many kJ you should eat per day.
Good to know
100 kcal is about 25 g of carbohydrate or protein, or 11.1 g of fat. Many portion-controlled snacks are sold at around this energy.
Nearby conversions
| Calories (kcal) | Kilojoules (kJ) |
|---|---|
| 1 kcal | 4.184 kJ |
| 50 kcal | 209.2 kJ |
| 100 kcal | 418.4 kJ |
| 200 kcal | 836.8 kJ |
| 250 kcal | 1,046 kJ |
Browse all popular conversions or the calories to kJ chart.
Frequently asked questions
How many kJ is 100 calories?
100 calories (kcal) is 418.4 kJ. Multiply 100 by 4.184 to check.
How many joules is 100 kcal?
100 kcal is 418,400 J, since 1 kcal is 4,184 J.
What percentage of a daily intake is 100 kcal?
About 5% of a 2,000 kcal reference day, or about 4.8% of the 8,700 kJ reference day.
Last updated 11 Oct 2026. How we calculate.