What is the difference between a calorie and a kilocalorie?

A kilocalorie (kcal) equals 1,000 small calories. Food labels use kilocalories — so "200 Calories" on a US label means 200 kcal, not 200 small calories.

How many kilojoules is 1 kilocalorie?

1 kcal = 4.184 kJ exactly (using the thermochemical definition). For practical nutrition purposes many sources round to 4.2 kJ.

Why do European labels show kJ instead of kcal?

EU regulations (Regulation 1169/2011) require energy to be declared in kJ first, followed by kcal in parentheses, because kJ is the SI unit for energy.

Is the conversion factor always 4.184?

The thermochemical kilocalorie uses exactly 4.184 kJ. The international table calorie uses 4.1868 kJ. The difference is tiny for nutrition purposes and 4.184 is the standard used on food labels.

Can I convert backwards — kJ to kcal?

Yes. Enter a kJ value in the lower field and the converter calculates kcal automatically. The formula is kcal = kJ ÷ 4.184.

Kilocalories to Kilojoules Converter

Convert food kilocalories (Calories) to kilojoules instantly — the unit shown on European and Australian nutrition labels.

Convert Energy Units

Enter a value in either field — the other updates instantly.

Kilocalories (kcal) — used on US & UK labels

kcal

Kilojoules (kJ) — used on EU & AU labels

Result

Enter a value on the left to see the result.

Common kcal → kJ Reference

kcal	kJ	Rough equivalent

Summary

This converter turns kilocalories (kcal) — the unit used on US and UK nutrition labels — into kilojoules (kJ), the SI energy unit required on labels in Europe, Australia, and New Zealand. The exact conversion factor is 1 kcal = 4.184 kJ. You can convert in both directions: enter kcal to get kJ, or enter kJ to get kcal.

How it works

Enter a kilocalorie (kcal) value in the top field.
The converter multiplies by 4.184 to produce kilojoules (kJ).
Or enter a kJ value in the bottom field to convert back to kcal.
Results update instantly as you type — no button press needed.
Use the Reset button to clear both fields.

Use cases

Read a US food label and find the kJ equivalent for an Australian recipe app.
Compare meal energy across labels in different countries.
Convert kcal targets from a US dietitian into kJ for a European food diary.
Check kJ values when travelling abroad where labels show kJ only.
Quickly convert daily calorie goals into kJ for science-class homework.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu