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What is a calorie?

The scientific gram calorie — 4.184 joules

Definition

The gram calorie (small calorie) equals 4.184 joules — the energy to raise 1 g of water by 1 °C. It is a scientific unit, distinct from the nutrition "Calorie" (kcal). Largely replaced by joules in modern science.

Common uses

  • Thermodynamics and older physics texts
  • Chemistry energy calculations
  • Some engineering heat-transfer contexts

🌍 Real-world scale

Raising 1 g of water 1 °C: 1 cal. A 100 kcal snack = 100,000 small calories.

Convert from calories

9 conversions
Calorie to Joule1 cal = 4.184 JCalorie to Kilojoule1 cal = 0.004184 kJCalorie to Megajoule1 cal = 4.1840e-6 MJCalorie to Kilowatt-Hour1 cal = 1.1622e-6 kWhCalorie to Watt-Hour1 cal = 0.001162 WhCalorie to Kilocalorie1 cal = 0.001 kcalCalorie to British Thermal Unit1 cal = 0.003966 BTUCalorie to Electronvolt1 cal = 2.6114e19 eVCalorie to Therm1 cal = 3.9657e-8 thm

Convert to calories

9 conversions
Joule to Calorie1 J = 0.239 calKilojoule to Calorie1 kJ = 239.006 calMegajoule to Calorie1 MJ = 239,005.74 calKilowatt-Hour to Calorie1 kWh = 860,420.65 calWatt-Hour to Calorie1 Wh = 860.421 calKilocalorie to Calorie1 kcal = 1,000 calBritish Thermal Unit to Calorie1 BTU = 252.164 calElectronvolt to Calorie1 eV = 3.8293e-20 calTherm to Calorie1 thm = 25,216,440.08 cal

Tips

  • 1 cal = 4.184 J. 1 kcal = 4184 J.
  • Scientific "calorie" and nutrition "Calorie" differ by 1000×.
  • Prefer joules in modern scientific writing.

Common mistakes

  • Assuming "calories" on food labels means gram calories — they are kcal.
  • Mixing gram calories and kilocalories in calculations.
  • Confusing calorie (energy) with calorimeter (apparatus).

FAQ about the calorie

What is a calorie?
The gram calorie (small calorie) equals 4.184 joules — the energy to raise 1 g of water by 1 °C. It is a scientific unit, distinct from the nutrition "Calorie" (kcal). Largely replaced by joules in modern science.
Where is the calorie used?
The calorie is commonly used for: Thermodynamics and older physics texts; Chemistry energy calculations; Some engineering heat-transfer contexts.
What is an example of a calorie in real life?
Raising 1 g of water 1 °C: 1 cal. A 100 kcal snack = 100,000 small calories.
What category does the calorie belong to?
The calorie is a unit of energy, part of the 10-unit energy category on UnitConv.
How accurate are calorie conversions?
All conversion factors follow NIST and BIPM international standards to 8 significant figures — the highest practical accuracy.
Explore all 10 energy units and their conversions.⚡ Energy hub →