Calories in, kilojoules out
One kilocalorie is 4.184 kilojoules. That’s the only number this tool needs. Type a kcal value and the kJ equivalent lands instantly, no submit step, no menu to navigate.
So a 200 kcal snack is 836.8 kJ. A 2000 kcal daily target is 8368 kJ. And a single 50 kcal yogurt comes out to 209.2 kJ. Multiply kcal by 4.184 and you’re done, since the relationship is a clean constant with no offset or formula.
When you’d actually need this
Here’s a thing that trips people up: the “Calorie” on a US or UK food label is really a kilocalorie. So if your fitness app, your recipe, or your diet plan counts in Calories but you need to log energy in kilojoules, this is the conversion that bridges them. A meal you logged as 650 Calories is 2719.6 kJ.
Diet tracking across regions is the common scenario. You might count calories day to day but then read a product made for the Australian or European market, where the headline figure is kJ. Converting the other direction (your kcal target into kJ) lets you compare apples to apples. A 1800 kcal cut translates to 7531 kJ, which you can then check directly against a kJ-labeled product.
Numbers you’ll reuse
A few of these cover most everyday needs:
- 100 kcal = 418.4 kJ
- 250 kcal = 1046 kJ
- 500 kcal = 2092 kJ
- 1000 kcal = 4184 kJ
- 2000 kcal = 8368 kJ
- 2500 kcal = 10460 kJ
That 2000 kcal line is the familiar daily reference in the US and UK, and it maps to 8368 kJ, close to the 8700 kJ figure Australian labels use. The tool’s table lays these out, with a free field for any other value.
How to use it
Enter a kilocalorie value and read the kilojoules as you type. There’s no button, the result just updates. The reference table below has common amounts pre-calculated, so for standard figures you can skip typing. Every calculation runs in your browser using the exact 4.184 factor, so nothing you enter is uploaded and it keeps working offline once the page loads.
For a rough head estimate, multiply kcal by 4 instead of 4.184. It undershoots the kJ a little (by about 4.4%), which is fine for a ballpark. When the exact figure matters, the tool applies the full constant.
FAQ
How many kJ in a kcal?
Exactly 4.184 kilojoules per kilocalorie. So you multiply your kcal figure by 4.184 to get kilojoules.
Is a Calorie the same as a kilocalorie?
Yes. The “Calorie” with a capital C on food labels is a kilocalorie (1000 small calories). So 200 Calories on a label means 200 kcal, which is 836.8 kJ.
What’s 2000 calories in kJ?
8368 kJ. Since label Calories are kilocalories, 2000 of them equals 2000 kcal, and multiplying by 4.184 gives 8368 kilojoules.
Why convert kcal to kJ at all?
Because much of the world labels food energy in kilojoules. If your tracking is in calories but a product or a regional guideline is in kJ, converting lets you compare them directly.
Does this send my data anywhere?
Nope. It’s plain browser math with the factor built in, so your numbers stay local and it runs offline after the page has loaded.