Multiply calories by 4.184
1 small calorie (cal) equals exactly 4.184 joules — defined by the International Steam Table convention. 1 food Calorie (kcal) equals 1000 small calories = 4184 joules = 4.184 kJ. The factor traces to early caloric experiments measuring water heating, later refined when the joule was defined in terms of mechanical work. The capital-C 'Calorie' on food labels is the same as 'kilocalorie' — different notations, same quantity.
Calories and joules both measure energy, just at different scales and from different traditions. The joule is the SI unit, defined as the energy from one watt over one second. The calorie comes from the older heat-science tradition: the energy needed to raise one gram of water by one degree Celsius.
One 'small' calorie (cal) equals 4.184 joules. The 'large' calorie used on food labels (Cal, kcal, or food calorie) equals 1000 small calories = 4184 joules.
ConvertBuddy treats input 'calories' as small calories by default — for food labels you typically convert kcal to kJ instead. Confusing the two factors of 1000 is the most common conversion mistake in nutritional and chemical contexts.
European food labels print both kcal and kJ values. US labels print only Calories (= kcal). Convert when comparing identical foods across regions or following imported recipes that quote energy in kJ.
Endurance athletes track intake in Calories; some scientific training literature uses kilojoules. 2000 Cal of daily diet = 8368 kJ. Convert when reading studies and translating recommendations to kitchen-label units.
Thermochemistry uses joules in SI; older textbooks and tables list ΔH in kcal/mol. Convert to keep enthalpy calculations consistent across mixed-source data.
Treadmills, stationary bikes, and rowers display energy burn in calories (meaning Calories = kcal). Some European models display kJ instead. Convert to compare workouts across machines.
Pet-food labels in the EU list ME (metabolizable energy) in kJ/100g; US labels list kcal/cup. Convert to compare brands on a per-energy basis when picking a portion-controlled diet.
1 calorie (small calorie) equals 4.184 joules. 1 food Calorie (kcal) equals 4,184 joules.
A small calorie (cal) heats 1g of water by 1°C. A food Calorie (Cal or kcal) is 1,000 small calories.