Convert kilocalories to kilojoules in one step. Type a value, change the units if you need a different pair, and the answer updates as you type, with the reverse rate and a quick reference list.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How to convert kilocalories to kilojoules
Multiply the number of kcal by 4.184 to get kJ:
kJ = kcal × 4.184
To go the other way, divide by 4.184 (or multiply by 0.239006). The converter stores each unit as a multiple of a base unit, so you can also pick any other pair of units from the same group.
Worked example
Using the default values in the converter above:
| Input | Value |
|---|---|
| Value | 2,000 |
| From | Kilocalories |
| To | Kilojoules |
2,000 kilocalories equals 8,368 kilojoules
Kcal to KJ reference table
| Kilocalories | Kilojoules |
|---|---|
| 1 kcal | 4.184 kJ |
| 10 kcal | 41.84 kJ |
| 100 kcal | 418.4 kJ |
| 500 kcal | 2,092 kJ |
| 1,000 kcal | 4,184 kJ |
| 2,000 kcal | 8,368 kJ |
| 2,500 kcal | 10,460 kJ |
| 5,000 kcal | 20,920 kJ |
| 10,000 kcal | 41,840 kJ |
Tips and common mistakes
The Calories on food labels are kilocalories (kcal), and the kilojoule (kJ) figure beside them is the same energy in metric terms: 1 kcal is 4.184 kJ. Many UK labels show both, so this is useful for checking them.
Electricity and gas bills use the kilowatt-hour (kWh), which is 3.6 million joules, or 3,600 kJ. A 1 kW heater running for one hour uses 1 kWh.
Note that a small calorie (cal) is a thousandth of a kilocalorie. Mixing the two up gives an answer that is 1,000 times out.
Frequently asked questions
How many kilojoules are in 1 kcal?
1 kcal equals 4.184 kilojoules.
How do I convert kcal to kJ by hand?
Multiply the kcal figure by 4.184. For example, 2,000 kcal × 4.184 = 8,368 kJ.
How do I convert kJ back to kcal?
Divide the kJ figure by 4.184, or multiply it by 0.239006. For example, 8,368 kJ is 2,000 kcal.
Is this conversion exact?
Yes. The kilocalorie is defined as 4.184 kJ and the kWh as 3.6 MJ, so the factors are exact apart from rounding.