Why We Built This Site
Food energy is measured in two units, and the world never agreed on one. Australia, New Zealand, South Africa and China label food in kilojoules. The United States and Canada use Calories. The UK and the European Union print both. Diet apps, fitness trackers, recipes and research papers pick whichever they like.
The result is a lot of people doing mental arithmetic in supermarket aisles, and a lot of confusion about what “Cal”, “kcal” and “kJ” really mean. kj to calories exists to fix that with fast, accurate, free tools and plain-English explanations.
What You’ll Find Here
- Converters for kJ to Calories and Calories to kJ that show the working, not just the answer.
- Calculators for daily kJ needs, macros to kJ, food labels and exercise burn.
- Reference charts for kJ to Calories, Calories to kJ and 120+ everyday foods.
- Installable app: the kJ to Calories converter app works offline on phones and computers.
- Guides on the blog covering labels, daily intake, weight management, drinks, fast food and exercise.
How We Keep Our Numbers Accurate
- One standard factor. Every conversion uses 1 kcal = 4.184 kJ, the thermochemical calorie used for food energy on labels and in nutrition science.
- Recognised formulas. Daily energy estimates use the Mifflin-St Jeor equation with standard activity factors. Exercise estimates use MET values from the Compendium of Physical Activities. Macro calculations use the energy factors applied on food labels (17, 37, 17, 8 and 29 kJ per gram).
- Transparent sources. Food values are typical figures based on USDA FoodData Central and common nutrition-panel values, rounded sensibly and always shown in both units.
- Worked examples. We show the maths so you can check any result yourself.
- Regular reviews. We re-check content and tools and update them when guidelines or data change. Each page shows when it was last updated.
What We Are Not
We’re not doctors or dietitians, and nothing on this site is personal medical advice. Our tools give general estimates for healthy adults. If you have a medical condition, are pregnant or breastfeeding, or are thinking about a big change to how you eat, please speak with a qualified health professional. See our disclaimer for details.
Get In Touch
Found an error, want a new calculator, or have a question about a conversion? We’d love to hear from you, visit the contact page or email Info@kjtocalories.org.