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Italiano1 kcal = 4.184 kJ: the formula
To convert kcal to kJ, multiply by 4.184: kJ = kcal × 4.184. The factor is exact, because the calorie used in nutrition is defined as 4.184 joules. Example: a 600 kcal meal provides 600 × 4.184 = 2,510.4 kJ.
The converter above opens on 1 kcal = 4.184 kJ. Type your number in "Value" and the answer appears at once. The "In every unit" table gives the same energy in calories, joules, watt-hours and BTU, and ⇄ "Swap units" switches to kJ to kcal.
Kcal to kJ chart
| kcal | kJ | Example |
|---|---|---|
| 1 | 4.184 | One kilocalorie |
| 4 | 16.74 | 1 g of carbohydrate or protein |
| 9 | 37.66 | 1 g of fat |
| 80 | 334.72 | A medium apple |
| 100 | 418.4 | A small snack |
| 250 | 1,046 | A chocolate bar |
| 500 | 2,092 | An hour of brisk cycling |
| 600 | 2,510.4 | A full meal |
| 2,000 | 8,368 | Daily value used on US labels |
| 2,500 | 10,460 | A very active day |
Labels, diets and workouts
Australia and New Zealand
Food labels there lead with kilojoules, and the reference is an average adult diet of 8,700 kJ a day, which is 2,079 kcal. If you count calories in a US or UK app, convert the label: a 1,200 kJ sandwich is 286.8 kcal.
Europe and the UK
Nutrition panels give both, kJ first: "Energy 1,464 kJ / 350 kcal". The reference intake for an adult is 8,400 kJ or 2,000 kcal.
Fitness trackers
Watches and apps show kcal, often labeled just "Cal". Some gym machines and cycling power meters report kJ of work done instead.
Mental math
Multiply by 4, then add 5%. For 350 kcal: 350 × 4 = 1,400, plus 70, gives 1,470 kJ against 1,464.4 exactly. Multiplying by 4 alone reads 4% low.
Frequently asked questions
Why don't the two numbers on my label match 4.184?
Labels work out kJ and kcal separately, with set factors for each nutrient: 37 kJ or 9 kcal per gram of fat, 17 kJ or 4 kcal per gram of carbohydrate and protein. Since 9 kcal is really 37.66 kJ, the ratio on a label shifts a little with the food.
Is a Calorie the same as a kcal?
Yes. A food Calorie, with a capital C, is one kilocalorie. A US label with 200 Calories means 836.8 kJ.
Why do cyclists say kJ and kcal are about the same?
A power meter counts the kJ of work sent to the pedals. Muscles turn only about a quarter of food energy into that work, so the body burns roughly four times as much. Four times the kJ, divided by 4.184 to get kcal, lands close to the original number: a 1,000 kJ ride costs about 1,000 kcal.