Convert calories kcal to kJ

One kilocalorie equals 4.184 kilojoules. To convert any number of kilocalories to kilojoules, 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 kcal to kJ formula

To go the other way, use kilocalorie = kilojoule ÷ 4.184.

About these units

The "calorie" on food labels is actually a kilocalorie — 1,000 small calories. One kilocalorie is 4.184 kilojoules.

The kilojoule is the energy unit on food labels outside the United States. One kilocalorie is 4.184 kilojoules, which is why the kJ figure on a packet is always the larger number.

Kilocalorie is also written kilocalories, calories, food calories and Cal. Kilojoule is also written kilojoules.

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.