Kilojoules to kilocalories converter

How to convert kJ to kcal

Divide the kilojoules by 4.184: kcal = kJ ÷ 4.184. The factor is the thermochemical calorie, defined as exactly 4.184 J (NIST SP 811, Appendix B). So 1,000 kJ is about 239 kcal, and the 8,700 kJ average adult diet used on Australian food labels is about 2,079 kcal. Use it to log a kJ label value in a calorie-counting app or to compare it with a kcal target.

kJ to kcal by hand

Because 4.184 kJ make one kcal, the kcal figure is always a little under a quarter of the kJ figure.

• 500 kJ: 500 ÷ 4.184 = 119.5 kcal
• 2,000 kJ: 2,000 ÷ 4.184 = 478.0 kcal
• 4,184 kJ: exactly 1,000 kcal

If you prefer to multiply, 0.239 is accurate to within 0.003%. Dividing by 4 makes a fast check but reads 4.6% high: 8,700 kJ gives 2,175 instead of 2,079 kcal.

kJ to kcal chart

The kcal values are rounded to six decimal places.

kJ on Australian, New Zealand and EU labels

Australian and New Zealand labels must give energy in kJ, and kcal is optional. Where a label shows percentage daily intake, it is based on that 8,700 kJ average diet, a little more than the 2,000 kcal behind US daily values.

EU labels print both units. Their reference intake for an average adult is 8,400 kJ or 2,000 kcal; the kJ figure is rounded, since 2,000 kcal is exactly 8,368 kJ.

Why a label's kcal can differ from your answer

EU rules work out each energy column from the nutrients (Regulation (EU) No 1169/2011, Annex XIV). Protein and carbohydrate count 17 kJ or 4 kcal per gram, and fat 37 kJ or 9 kcal, ratios of 4.25 and about 4.11 instead of 4.184.

So 100 g of carbohydrate counts as 1,700 kJ and 400 kcal, although 1,700 ÷ 4.184 = 406.3 kcal. 100 g of fat counts as 3,700 kJ and 900 kcal, although 3,700 ÷ 4.184 = 884.3 kcal.

When a label prints both units, copy its kcal figure instead of converting the kJ.

Common mistakes

• Multiplying instead of dividing. 8,700 × 4.184 = 36,400.8, over four times the kJ figure. The kcal answer must be the smaller number.
• Mixing up joules and kilojoules. Physics problems often give energy in joules. 1,000 J is 1 kJ, or 0.239 kcal; treating it as 1,000 kJ makes the answer 1,000 times too large.
• Reading a bike computer's kJ as food energy. A power meter's kJ is the work delivered to the pedals. Converting 800 kJ of work gives 191.2 kcal, but your body burned several times that much food energy to produce it.

Related conversions

Use kcal to kJ for the reverse step and the energy converter for joules, watt-hours or BTU. To compare a kJ intake with your daily needs, the BMR and TDEE calculator estimates them in kcal.