Energy converter

Joules to Watt-hours Calculator

Convert energy in joules to watt-hours, kilowatt-hours, and kilojoules.

How Joules to Wh works

A watt-hour is the energy of one watt sustained for one hour. Since one watt is one joule per second and an hour is 3,600 seconds, one watt-hour equals 3,600 joules.

To convert joules to watt-hours, divide by 3,600. This is the natural way to express battery and energy-storage capacities, which are almost always rated in watt-hours or kilowatt-hours rather than joules.

Formula

1Wh = J ÷ 3,600

1 Wh = 3,600 J; 1 kWh = 3,600,000 J.

Joules to Wh conversion table

Reference Table5 rows

Common joule values converted to watt-hours.
Joules↕	Watt-hours↕	Kilowatt-hours↕
3,600 J	1 Wh	0.001 kWh
36,000 J	10 Wh	0.01 kWh
360,000 J	100 Wh	0.1 kWh
3,600,000 J	1,000 Wh	1 kWh
18,000,000 J	5,000 Wh	5 kWh

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FAQ: Joules to Wh

How many joules are in a watt-hour?

One watt-hour equals exactly 3,600 joules. This is one watt (one joule per second) sustained for 3,600 seconds (one hour).

How do you convert joules to watt-hours?

Divide the energy in joules by 3,600. For example, 18,000 J ÷ 3,600 = 5 Wh.

Why are batteries rated in watt-hours not joules?

Watt-hours align with how power (watts) and time (hours) are used in everyday life, giving more manageable numbers than joules for storage capacity.

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