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Calories to Kilojoules Converter

Convert food calories to kilojoules instantly, with a reference table for exercise, meals and daily targets.

Calories to KJ Converter

1 kcal = 4.18 kJ

Multiply calories by 4.184 to get kilojoules.

The link carries the values you entered, so whoever opens it sees the same result. Nothing is stored on our side — the numbers travel in the link itself.

Calories to kilojoules reference table

The conversions people look up most often, rounded to 2 decimal places.

Common calories to kilojoules conversions
Calorie (kcal)Kilojoule (kJ)
50 kcal209.2 kJ
100 kcal418.4 kJ
200 kcal836.8 kJ
250 kcal1,046 kJ
400 kcal1,673.6 kJ
500 kcal2,092 kJ
800 kcal3,347.2 kJ
1,000 kcal4,184 kJ
1,500 kcal6,276 kJ
2,000 kcal8,368 kJ
2,500 kcal10,460 kJ
3,000 kcal12,552 kJ

The calories people look up most

150 kcal = 627.6 kJ
A banana and a half, or about thirty minutes of brisk walking.
500 kcal = 2,092 kJ
A substantial meal, and the daily deficit most weight-loss advice starts from.
800 kcal = 3,347.2 kJ
A large restaurant main course on its own, before anything ordered alongside it.
1,500 kcal = 6,276 kJ
A restrictive daily intake, below the level most authorities advise without supervision.
2,000 kcal = 8,368 kJ
The US daily reference value, against the 8,700 kJ Australia prints on its labels.

How the calories to kj calculation works

A food calorie is exactly 4.184 kilojoules:

kilojoules = calories (kcal) × 4.184

The joule is the SI unit of energy; the calorie is a survival from an older system, defined as the energy needed to raise one gram of water by one degree Celsius. The 4.184 figure is the mechanical equivalent of heat, measured by Joule in the 1840s and now fixed by definition.

Everything below uses the food calorie (kcal), which is what appears on a label.

Meals and targets:

  • 500 kcal → 2,092 kJ
  • 2,000 kcal → 8,368 kJ — the US daily reference
  • 2,500 kcal → 10,460 kJ
  • 3,000 kcal → 12,552 kJ

Exercise, which is where the number is most often misread:

  • 30 minutes of brisk walking, ~150 kcal → 628 kJ
  • An hour of cycling, ~500 kcal → 2,092 kJ
  • A marathon, ~2,600 kcal → 10,878 kJ

A useful piece of perspective: a pound of body fat stores roughly 3,500 kcal, or 14,644 kJ. That is why a 500 kcal daily deficit is the standard advice for losing about a pound a week — and why an hour of exercise, at 400–600 kcal, does not offset a large meal.

Why some countries lead with kilojoules. Australia and New Zealand mandate kJ on labels because it is the SI unit and avoids the calorie/kilocalorie ambiguity entirely. There is no "kilo-kilojoule" confusion to have.

Frequently asked questions

Why do labels give both a per-100 g and a per-serving figure?

Because the two answer different questions. The per-100 g column lets you compare products directly, while the per-serving column describes what you will actually eat - and the serving size is the manufacturer’s choice. A cereal at 1,600 kJ per 100 g, or 382 kcal, looks moderate at a 30 g serving of 480 kJ, and very few people pour 30 g.

How much energy is in alcohol?

Seven kilocalories a gram, which is 29 kJ - closer to fat than to carbohydrate, and the reason drinks add up faster than their size suggests. A pint of 4% beer is around 180 kcal, or 750 kJ, and a 175 ml glass of 13% wine about 160 kcal, or 670 kJ. EU labels are not required to break down the energy in drinks above 1.2% alcohol, so the figure is often an estimate.

How does a daily calorie intake compare with a kilowatt-hour?

One kilowatt-hour is 3,600 kJ, so a 2,000 kcal day - 8,368 kJ - is 2.32 kWh. That is roughly what a domestic oven draws in an hour or so, which makes a useful piece of perspective on how little energy a human body actually runs on. Nothing about the way the body uses that energy resembles an oven, but the units are the same.

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Further reading