Calories (kcal) vs Kilojoules (kJ)
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
UK food labels, US food labels, fitness apps, restaurant menus (UK calorie labelling law since 2022).
EU food labels (required since 1990), Australia/NZ food labels, scientific/physics work.
| Aspect | Calories (kcal) | Kilojoules (kJ) |
|---|---|---|
| Per medium banana | ≈ 105 kcal | ≈ 439 kJ |
| Per Big Mac | ≈ 563 kcal | ≈ 2,356 kJ |
| UK daily target (adult, female) | 2,000 kcal | 8,368 kJ |
| UK daily target (adult, male) | 2,500 kcal | 10,460 kJ |
| Conversion | ×4.184 → kJ | ÷4.184 → kcal |
Frequently asked
Why does the EU lead with kJ?
kJ is the SI unit of energy. EU directive 1990 required SI units for food labelling, with kcal allowed alongside but not as primary. UK kept kcal as primary post-Brexit.
Is the 'calorie' on US food labels actually a calorie?
No — it's a kilocalorie. The convention of capital C 'Calorie' = 1000 'calories' is historical and confusing. In practice everyone treats food 'Calories' (capital) = kcal, and very few people use small calories in everyday language.
Frequently asked questions
Why does the EU lead with kJ?
kJ is the SI unit of energy. EU directive 1990 required SI units for food labelling, with kcal allowed alongside but not as primary. UK kept kcal as primary post-Brexit.
Is the 'calorie' on US food labels actually a calorie?
No — it's a kilocalorie. The convention of capital C 'Calorie' = 1000 'calories' is historical and confusing. In practice everyone treats food 'Calories' (capital) = kcal, and very few people use small calories in everyday language.