Units: kcal, kJ and grams to energy

Two conversions that come up every time you read a label or a study. Everything is computed in your browser.

Kilocalories and kilojoules

One kilocalorie is 4.184 kilojoules. Labels in the EU show both; a "calorie" in everyday speech is a kilocalorie, and the app uses kilocalories throughout.

Grams to energy

Labels convert grams to energy with fixed factors set by regulation: 4 kcal (17 kJ) per gram of protein or carbohydrate, 9 kcal (37 kJ) per gram of fat, 2 kcal (8 kJ) per gram of fibre and 7 kcal (29 kJ) per gram of alcohol. Type the grams and the calculator shows each one's energy and its share of the total — which is how "30 percent of energy from fat" turns back into grams for a given day.

Two things to know. The factors are rounded conventions, so a label's energy line rarely equals the sum you compute to the calorie; a few percent either way is the rounding, not an error. And fibre is counted at 2 kcal on EU labels but was ignored, or counted at 4, under older conventions, which is one reason values for the same food differ between databases.

In the app

The app stores nutrition per hundred grams from source-backed data and applies these factors when it checks a menu's macros against the day's target; it does not recompute energy from macros where the source gives energy directly.

Sources

EU Regulation 1169/2011, Annex XIV — official regulation
Limitation: labelling convention, не physiological absorption model

Educational information, not medical advice. It does not replace a consultation with a doctor or a registered dietitian. Not for people under 18, during pregnancy or breastfeeding, or with a history of an eating disorder — talk to a professional first.