How many joules are in one food Calorie?

One food Calorie equals one kilocalorie (kcal), which is 4184 joules. A nutrition-label Calorie is always a kilocalorie, even though it is written with a capital C.

Why is the food Calorie a kilocalorie?

The "Calorie" on food packaging (capital C) is 1000 small calories. To avoid confusion this tool labels it Cal (kcal) and converts at 4184 J per Calorie.

How do I convert joules to food Calories?

Divide the energy in joules by 4184. For example 4184 J is 1 food Calorie, and 2,092,000 J is 500 Cal. To go the other way, multiply Calories by 4184.

How do I convert kilojoules (kJ) to Calories?

Multiply the joule result by 1000 first if you have kilojoules, or simply remember that 1 kJ is about 0.239 food Calories. A label showing 1046 kJ is roughly 250 Cal.

Is the food Calorie the same as the calorie used in physics?

No — the food Calorie (kcal) is 1000 times the small thermochemical calorie. The small calorie is 4.184 J; the food Calorie is 4184 J. This tool uses the food Calorie.

How many joules are in a typical meal?

A 600 Cal meal contains 600 × 4184 = 2,510,400 joules. Daily intakes of around 2000 Cal equal roughly 8,368,000 J, or 8368 kJ.

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Joules to Food Calories Converter

Joules to food Calories — nutrition-label energy

The energy on a nutrition label is given in Calories (with a capital C), and that food Calorie is really a kilocalorie. This converter changes joules into the Calories shown on food packaging, and back again, so you can compare a scientific energy figure in joules with the value printed on a wrapper.

How it works

The conversion uses one exact constant:

1 food Calorie (kcal) = 4184 J

Joules to Calories: divide the joules by 4184.
Calories to joules: multiply the Calories by 4184.

The capital-C “Calorie” used in nutrition equals 1000 small thermochemical calories (each 4.184 J), which is why the multiplier is 4184 rather than 4.184. If your label is in kilojoules, divide the joule result by 1000 to get kJ.

Food Calories (kcal)	Joules
100	418,400 J
250	1,046,000 J
500	2,092,000 J
2000	8,368,000 J

Example

A 250 kcal snack contains 250 × 4184 = 1,046,000 J of energy — equivalently 1046 kJ. Going the other way, 2,092,000 J entered as joules returns 500 Cal.

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