One (food) calorie is equal to about 4.184 kilojoules, so to convert calories to kilojoules you multiply by 4.184.

Quick scoop

  • 1 calorie (kcal) ≈ 4.184 kilojoules (kJ).
  • Example: 100 calories ≈ 100×4.184=418.4100×4.184=418.4100×4.184=418.4 kJ.
  • To go the other way, kJ → calories, divide kilojoules by 4.184.

In everyday nutrition labels, the “calories” you see are actually kilocalories, and each of those is about 4.184 kJ of energy.

TL;DR: Multiply calories by 4.184 to get kilojoules; divide kilojoules by 4.184 to get calories.

Information gathered from public forums or data available on the internet and portrayed here.