Kilojoules and kilocalories
A kilojoule is 1,000 joules. Food energy in Australia, New Zealand and the EU is labeled in kilojoules alongside kilocalories.
A kilocalorie is 1,000 calories, exactly 4,184 joules: the food Calorie. Nutrition labels, diet apps and fitness trackers count energy in kcal.
Worked example
Convert 1,000 kJ: 1,000 × 0.2390057361 = 239.0057361, so 1,000 kilojoules is 239.0057361 kilocalories. Likewise 2,000 kJ = 478.0114723 kcal.
Estimating in your head
Divide by 4.2 for a quick figure; it is off by about 0.4%. For 1,000 kJ that gives 238 kcal, against 239.006 exactly.
Going the other way
To convert kilocalories to kilojoules, divide by 0.2390057361 (or multiply by 4.184). The swap button between the boxes opens that page.
How this works
kcal = kJ × 0.2390057361
1 kJ = 1,000 J and 1 kcal = 4,184 J, both by definition, so the factor is their ratio: 0.2390057361 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many kilocalories are in a kilojoule?
1 kilojoule = 0.2390057361 kilocalories. The factor is exact by definition but has endless decimals, so it is shown rounded; the page uses the full value.
How do I convert kilojoules to kilocalories?
Multiply by 0.2390057361. For example, 2,000 kJ × 0.2390057361 = 478.0114723 kcal.
What is 10,000 kJ in kilocalories?
10,000 kJ = 2,390.057361 kcal. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- BIPM — The International System of Units (SI Brochure), 9th edition
- Wikipedia — Calorie
Reviewed Oct 17, 2026 · test vectors fixtures/units/energy/kj-to-kcal/