⚖️ Comparison · Updated for 2026

Calories (kcal) vs Kilojoules (kJ)

Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.

Quick answer: 1 kcal = 4.184 kJ exactly. The 'calorie' on food labels (capital C) is actually a kilocalorie — 1000 small calories. EU food labels show both kcal and kJ; UK labels also show both kJ and kcal. Australian and NZ labels lead with kJ. A 2,000 kcal day = 8,368 kJ.
Decision guide — when to use which
Use Calories (kcal) when…

UK food labels, US food labels, fitness apps, restaurant menus (UK calorie labelling law since 2022).

Use Kilojoules (kJ) when…

EU and UK food labels (kJ required alongside kcal), Australia/NZ food labels, scientific/physics work.

📊 Side-by-side comparison
Aspect Calories (kcal) Kilojoules (kJ)
Per medium banana ≈ 105 kcal ≈ 439 kJ
Per Big Mac ≈ 500 kcal ≈ 2,090 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

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Why does the EU lead with kJ?

kJ is the SI unit of energy. EU food labelling rules require energy in kJ and kcal, with kJ conventionally listed first. UK law retained this, so UK labels show both, though UK consumers mostly look at kcal.

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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.

Reviewed for 2026. This comparison is general guidance based on publicly available information. Prices, rates, rules and specifications change, so check current details with the provider or an official source before making a decision. Built by a UK-based qualified primary teacher and FA Level 2 coach as part of 247QuickTools' free utility-tools project. We don't sell SEO links or accept paid placements in this content.

Frequently asked questions

Why does the EU lead with kJ?

kJ is the SI unit of energy. EU food labelling rules require energy in kJ and kcal, with kJ conventionally listed first. UK law retained this, so UK labels show both, though UK consumers mostly look at kcal.

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.