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Kilojoules to calories converter

Convert a food-label or nutrition-app energy value between kilojoules (kJ) and kilocalories (kcal) without estimating personal energy needs or judging the food.

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Calculate your result

Enter the number from the food label, recipe, menu or nutrition app. Do not add thousands separators; use a full stop when a comma with three following digits could be ambiguous.

Accepted range: 0 to 1000000 kJ

Your result will appear here

Nothing is saved or added to the URL.

What this result means

Choose the unit you have, enter the energy value, and the converter will show the same amount of food energy in the other unit. One nutritional Calorie is one kilocalorie (kcal), equal to exactly 4.184 kilojoules (kJ). [1][2]

What kJ, kcal and Calories mean

Kilojoules (kJ) and kilocalories (kcal) are two units for the same quantity: energy. In food and nutrition, one Calorie with a capital C is one kilocalorie. It is 1,000 small scientific calories. [1][2]

Why the factor is 4.184

NIST lists the thermochemical calorie as 4.184 joules. Scaling both units by 1,000 gives exactly 4.184 kilojoules for one kilocalorie. That is why kJ is divided by 4.184 to get kcal, and kcal is multiplied by 4.184 to get kJ. [1]

Why food labels use different units

Food Standards Australia New Zealand says nutrition panels provide energy in kilojoules or in kilojoules and kilocalories. The UK NHS explains that pre-packed food labels show both kJ and kcal. A converter is useful when a label, recipe or app uses only one of them. [2][3]

Keep the serving basis with the number

Converting the unit does not convert per serving into per 100 g, or change a serving into the amount you actually ate. Compare values only when the serving basis is the same. Label energy may already be an average and rounded before you enter it. [2][3]

What this conversion cannot tell you

The converted value cannot tell you how much energy you personally need or whether a food is nutritious. Personal needs and food choices require more context than one energy number, so this page deliberately provides no target, deficit or food rating. [4]

Formula and assumptions

Formula
kcal = kJ ÷ 4.184. kJ = kcal × 4.184. On food labels, a Calorie with a capital C means one kilocalorie (kcal), not one small scientific calorie. [1][2][3]
Version
Thermochemical kilocalorie and kilojoule conversion, nist-food-energy-kj-kcal-v1
Rounding
Calculate with the exact 4.184 kJ-per-kcal relationship and round once for display to two decimal places. The original label or app may use different display rounding.
Worked example
For a label showing 1,000 kJ: 1,000 ÷ 4.184 = 239.0057 kcal, displayed as 239.01 kcal. For 200 kcal: 200 × 4.184 = 836.8 kJ. [1]

Who this is for — and when not to use it

Intended use

Neutral, reversible conversion of food energy between kilojoules (kJ) and nutritional Calories or kilocalories (kcal), including values from food labels, recipes, menus and nutrition apps.

Not intended for

This tool does not estimate energy needs, prescribe a calorie target, judge food quality, calculate a deficit, predict weight change, or provide nutrition or medical advice.

Exclusions

  • Personal daily-energy or weight-change calculations
  • Food-quality, diet or portion recommendations
  • Exercise-energy expenditure estimates
  • Small scientific calories (cal) rather than nutritional kilocalories (kcal)
  • Changing the serving size or correcting the source label

Evidence sources

  1. 1. Guide for the Use of the International System of Units (SI), NIST Special Publication 811 — National Institute of Standards and Technology. Accessed Aug 9, 2026.
  2. 2. Nutrition information panels — Food Standards Australia New Zealand. Accessed Aug 9, 2026.
  3. 3. Food labels — National Health Service. Accessed Aug 9, 2026.
  4. 4. Dietary energy — Eat For Health, Australian Government. Accessed Aug 9, 2026.