Quick answer
1 kcal = 4.184 kJ. Multiply 1 by 4.184 to check: 1 × 4.184 = 4.184.
How to convert 1 calories to kJ
- Start with 1 calories (kcal).
- Multiply by 4.184: 1 × 4.184 = 4.184 kJ.
- For joules, multiply by 4,184: that gives 4,184 J.
You may also see this searched as 1 cal to kj or 1 calories to kilojoules. A small calorie (cal) is different: 1 cal is 0.004184 kJ. Food labels almost always mean kcal. See the calories to kJ converter for more.
1 kcal in context
- less than 0.1% of the 8,700 kJ average-adult reference day on Australian and New Zealand labels.
- less than 0.1% 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
One kilocalorie is exactly 4.184 kJ. One small calorie (cal) is 4.184 joules, a thousand times less.
Nearby conversions
Browse all popular conversions or the calories to kJ chart.
Frequently asked questions
How many kJ is 1 calories?
1 calories (kcal) is 4.184 kJ. Multiply 1 by 4.184 to check.
How many joules is 1 kcal?
1 kcal is 4,184 J, since 1 kcal is 4,184 J.
What percentage of a daily intake is 1 kcal?
About less than 0.1% of a 2,000 kcal reference day, or about less than 0.1% of the 8,700 kJ reference day.
Last updated 11 Oct 2026. How we calculate.