Convert Kilocalories to Joules
Kilocalories to joules is the conversion you need when a food or nutrition figure is given in Calories but you want it in the SI unit of energy. One kilocalorie is exactly 4184 joules, so the joule number always comes out much larger.
Kilocalories to Joules conversion table
| Kilocalories (kcal) | Joules (J) |
|---|---|
| 1 | 4,184 |
| 2 | 8,368 |
| 3 | 12,552 |
| 5 | 20,920 |
| 10 | 41,840 |
| 20 | 83,680 |
| 50 | 209,200 |
| 100 | 418,400 |
| 500 | 2,092,000 |
| 1,000 | 4,184,000 |
The formula
To convert kilocalories to joules, multiply the number of kilocalories by 4184:
joules = kilocalories × 4184
A worked example
Say you have a 500 kcal meal — 500 food Calories — and want it in joules:
500 × 4184 = 2,092,000 J
So 500 kilocalories is exactly 2,092,000 joules.
Why the number is exact
A "kilocalorie" (kcal) is the "Calorie" you see on food nutrition labels — one food Calorie is one kilocalorie. It's built on the thermochemical calorie, which is defined as exactly 4.184 joules. A kilocalorie is 1000 of those, so it comes to exactly 4184 joules — a fixed definition, not a rounded measurement.
When you'll use it
Turning a food or nutrition Calorie count into the SI unit of energy, checking physics and chemistry homework that mixes calories and joules, and comparing energy figures that are quoted in different units.
Frequently asked questions
How many joules are in a kilocalorie?
Exactly 4184 joules. A kilocalorie uses the thermochemical calorie, which is defined as exactly 4.184 joules, so a kilocalorie — 1000 of them — is exactly 4184 joules.
Is a kilocalorie the same as a food Calorie?
Yes. The 'Calorie' with a capital C on a nutrition label is a kilocalorie — one food Calorie is one kilocalorie. So a 500-Calorie meal holds 500 kilocalories, which is exactly 2,092,000 joules.
Is the kilocalories to joules conversion exact?
Yes. The thermochemical calorie is defined as exactly 4.184 joules, so a kilocalorie is exactly 4184 joules — nothing is rounded away.