How the energy converter works

Enter an energy value in thermochemical calories or joules. The second field updates immediately, and the swap control reverses the conversion.

One small calorie is exactly 4.184 joules

The calculator uses the thermochemical calorie, written with a lowercase cal. Its relationship with the SI unit joule is exact:

1\,\mathrm{cal}=4.184\,\mathrm{J}

Multiply calories by 4.184 to get joules. Divide joules by 4.184 for the reverse calculation.

Conversions you can check by hand

1 cal = 4.184 J. This is the defining conversion factor.
100 cal = 418.4 J. Move directly by multiplying by 4.184.
250 cal = 1046 J. The result is an exact whole number.
418.4 J = 100 cal. Divide by 4.184 when starting with joules.

Food Calories use a larger unit

A capital-C Calorie on a food label normally means one kilocalorie, or 1000 small calories. Therefore 1 kcal equals 4184 J, not 4.184 J.

This tool changes units only. It does not estimate food energy, exercise expenditure or measurement uncertainty, and it does not turn extra displayed digits into extra accuracy.

Questions about calories and joules

The symbol and context tell you which calorie is meant.

How many joules are in one calorie?

One thermochemical calorie is exactly 4.184 joules.

How do I convert joules to calories?

Divide the joule value by 4.184.

Is a food Calorie the same as a calorie?

Not in common nutrition usage. One food Calorie is one kilocalorie, equal to 1000 cal or 4184 J.

What is 1 joule in calories?

One joule is approximately 0.239005736 thermochemical calories.

Does the converter use an exact factor?

Yes. It uses the defined thermochemical relation 1 cal = 4.184 J.

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Calcopedia (en) → Calories to joules

Calories to joules converter