Kilocalorie (kcal) to Kilojoule (kJ)
Convert kilocalories to kilojoules. US food labels list energy as Calories (capital C, equal to kilocalories) and rarely show kilojoules. One kilocalorie is exactly 4.184 kilojoules.
Frequently asked questions
1 kilocalorie (kcal) equals 4.184 kilojoules (kJ). This is an exact definition: 1 cal = 4.184 J, so 1 kcal = 4.184 kJ. US nutrition labels call kilocalories "Calories" (capital C).
The US Dietary Guidelines suggest approximately 8,370 kJ (2,000 Calories) per day for an average adult — the value shown as "% Daily Value" on US nutrition labels. Individual needs vary by age, sex, and activity level.
Multiply the number of Calories (kcal) by 4.184. Example: 500 Calories × 4.184 = 2,092 kJ. For a quick mental estimate, multiply by 4 then add roughly 18%.
The US uses the kilocalorie — branded as the "Calorie" (capital C) — as the primary unit on Nutrition Facts labels. Kilojoules are not required and are rarely shown. This contrasts with UK and EU labels, which must list kJ as the primary unit alongside kcal.