Calorie (cal)

Definition

The thermochemical calorie, exactly 4.184 joules.

History

The calorie was defined in the nineteenth century as the heat needed to raise one gram of water by one degree Celsius; the thermochemical calorie is now fixed at exactly 4.184 joules.

Where it is used

Calories are used in chemistry and to describe small amounts of energy; food labels use the larger kilocalorie.

Typical uses include chemistry, small energy amounts.

Conversion pages

These pages convert calorie to or from another unit in energy.

• Calorie to joule

Other Energy units

• Kilocalorie (kcal)
• Kilojoule (kJ)
• Joule (J)
• Kilowatt-hour (kWh)
• British thermal unit (BTU)
• Watt-hour (Wh)

Sources

• NIST SP 811 NIST SP 811, Appendix B; ISO 80000-5 (energy) · Dataset reviewed Nov 11, 2026