Convert calories to joules

One calorie equals 4.184 joules. To convert any number of calories to joules, multiply by 4.184.

The converter above works in both directions and updates as you type. Below you will find the formula, a worked example and a reference table of common values.

Energy conversions sit between physics and the kitchen. The joule is the SI unit and the one every equation uses; the calorie survives on food labels, where it is actually a kilocalorie a thousand times larger than the physicist’s calorie; and the kilowatt-hour is what an electricity meter counts. All three measure the same quantity, which is why an appliance’s consumption and a meal’s energy content can, in principle, be compared directly.

calories to joules formula

To go the other way, use calorie = joule ÷ 4.184.

About these units

The small calorie is the energy needed to warm one gram of water by one degree Celsius. It is a thousand times smaller than the "calorie" on a food label, which is really a kilocalorie.

The joule is the SI unit of energy: one newton acting over one metre, or one watt for one second. Every other energy unit here is defined against it.

Calorie is also written calories and cals. Joule is also written joules.

Sources

1. NIST Special Publication 811, Guide for the Use of the International System of Units (SI), 2008 edition — conversion factors for units outside the SI.