Kilojoules to Calories Converter

How the conversion works

The food calorie — technically a kilocalorie (kcal) — is defined as exactly 4.184 kilojoules, so the conversion is a single division or multiplication:

• kJ → kcal: divide by 4.184 — 2,000 kJ ÷ 4.184 = 478 kcal
• kcal → kJ: multiply by 4.184 — 250 kcal × 4.184 = 1,046 kJ

For quick head math, divide kilojoules by about 4.2 — or just by 4 if you only need a ballpark. A 900 kJ muesli bar is a bit over 200 calories; a 2,500 kJ meal is around 600.

One naming trap: the "calorie" on food labels and in diet apps is always the kilocalorie. This converter uses kcal throughout, so results match what any nutrition label or fitness tracker means by "calories".

Quick reference table

How to use it

1. Type a value into either field — kilojoules or calories.
2. The other side converts live; results are trimmed to one decimal.
3. Tap a common value chip (100 to 8,700 kJ) to start from a typical food-label amount.
4. Copy puts the full conversion (e.g. 2000 kJ = 478 kcal) on your clipboard.

When you need this

The classic case is Australian and New Zealand food labels: both countries print energy in kilojoules, while most of the world — and most diet apps — thinks in calories. Australian labels also frame portions against 8,700 kJ, the reference average adult daily intake, which works out to about 2,079 calories. If you're traveling, tracking macros in an app that expects kcal, or comparing an imported product against local ones, converting the label once puts everything on the same scale.

The same conversion turns up on gym equipment (some machines display kJ), in nutrition science papers and on European labels that list both units. To figure out what your own daily energy target should be, the TDEE Calculator estimates your maintenance calories, and the BMI Calculator puts your weight and height in context.

Private by design

The conversion runs in your browser — nothing is uploaded or tracked, and there's no sign-up. For other unit pairs, the general Unit Converter covers length, weight, volume, temperature and more, or browse more free utilities on the all tools page.