Kilojoules to Calories Converter

1 kcal equals exactly 4.184 kJ. This is the thermochemical calorie, the value used by food regulators worldwide (FDA, EFSA, FSANZ). To go from kJ to kcal, divide by 4.184; to go from kcal to kJ, multiply by 4.184. For a quick mental shortcut, divide kJ by 4.2 (close enough for menu reading).

No, and that is where most confusion comes from. A lowercase calorie (cal) is the small calorie: the energy to raise 1 g of water by 1 C, equal to 4.184 J. A capital-C Calorie is the food Calorie, which is 1,000 small calories, equal to 1 kcal or 4,184 J. Nutrition labels almost always mean food Calories even when they print 'calories', so 200 'calories' on a granola bar is 200 kcal, not 200 cal.

Australia, New Zealand, and the EU mandate kJ as the primary energy unit on nutrition panels (kcal is allowed as a secondary value). The US, Canada, and most of Latin America use 'Calories' (kcal) as the only printed unit. The underlying energy is identical: a 100 g chocolate bar at 2,250 kJ in Sydney is the same 538 kcal as in New York. The label difference is regulatory, not physical.

Because the word means two different things depending on capitalization, and almost no one notices the capital. A scientist's calorie (cal) is 4.184 J. A dietitian's Calorie (Cal) is 4,184 J, a thousand times bigger. To avoid the trap, nutrition writing now leans on kcal (unambiguously 4,184 J) or kJ. If a label or fitness tracker says 'calories' without context, assume it means kcal (food Calories), which is the convention in everyday US English.

A Big Mac is about 540 kcal, which equals 2,260 kJ (540 multiplied by 4.184). On an Australian or EU label it would be printed as 2,260 kJ with 540 kcal in smaller text; on a US label, 540 Calories. A banana is the lighter reference: 105 kcal or 439 kJ.