Energy Converter

Convert energy between joules, small calories, kilowatt-hours, and British Thermal Units. Enter the Value, select the From unit, choose the To unit, and the form returns the converted energy plus equivalents in all supported units. It is useful for physics, electricity bills, heating calculations, appliance use, and comparing energy units across disciplines.

Conversion factors

The calculator converts through joules and uses these factors exactly:

1 Wh = 3,600 J
1 kWh = 3.6 million J
1 food Calorie = 1 kcal

The current form supports small calories, not food Calories, and uses 1 cal = 4.184 J, 1 kWh = 3,600,000 J, and 1 BTU = 1,055.06 J.

For example, 2 kWh equals 2 × 3,600,000 = 7,200,000 J. Dividing by 1,055.06 gives about 6,824.28 BTU.

Common energy references

Energy is not the same as power. Use the power converter for watts, the electricity cost calculator for bills, and the battery charge time calculator for charging estimates.