What is the SI unit of heat?

Concept

Heat is energy transferred between systems because of a temperature difference.

In the International System of Units (SI), every form of energy, including heat, is measured in the joule (J).

Application

The question asks for the SI unit used to measure heat. Because heat is an energy transfer, its SI unit is the joule (J).

Contrast

• A calorie is a non-SI unit of heat.

• A kilocalorie equals 1,000 calories and is also non-SI.

• An erg is an energy unit in the centimetre–gram–second (CGS) system.

Cross-check

One joule has the SI base-unit form 1 kg·m2·s−2, confirming that the joule is the SI energy unit.

Result

Therefore, the SI unit of heat is the joule (J).