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.
Multiply small calories (cal) by 4.184. Multiply food Calories (Cal = kcal) by 4184. So 100 cal = 418 J; 100 Cal (food label) = 418,400 J = 418 kJ.
Notationally they are confusing. The Calorie with a capital C used on food labels is actually one kilocalorie (1000 small calories). When in doubt about a nutrition label: a 200 'calorie' yogurt is 200 kcal = 836,800 J = 836.8 kJ.
1 small calorie equals 4.184 joules exactly. 1 food Calorie (kcal) equals 4184 joules = 4.184 kilojoules.
European Union law requires both kcal and kJ on nutrition labels. Most of the world prefers kJ since it is the SI unit; the US sticks with kcal alone for consumer familiarity.
1 kJ equals 239 small calories or 0.239 food Calories. A 1000 kJ snack contains 239 Calories (kcal). Multiply kJ by 0.239 to read European labels in US convention.
Yes by a factor of 1000. The capitalization convention dates to the late 1800s when nutritionists chose to use the kilocalorie as their working unit and capitalized 'Calorie' to distinguish it. Casual writing rarely respects the distinction; food labels always mean kilocalorie.
The joule is the SI unit of energy, defined as the work done by one newton acting over one metre, or equivalently one watt-second. The calorie predates SI and was originally tied to the heat capacity of water. The 4.184 conversion factor reconciles the two definitions to high precision.
Two slightly different calorie definitions exist. The IT (International Table) calorie equals exactly 4.1868 J. The thermochemical calorie equals exactly 4.184 J. The 0.07% difference rarely matters in everyday use; nutrition and physiology use thermochemical by convention. ConvertBuddy uses 4.184.