Energy Converter
Convert between pJ, nJ, µJ, mJ, J, kJ, MJ, Wh, kWh. Free, with no limits and no account needed.
About Energy Units
Energy is measured in joules (J), with watt-hours (Wh) common for batteries — one watt sustained for one hour.
Energy ties power to time. Batteries are rated in watt-hours or milliamp-hours, while capacitor and component energy is usually in joules or millijoules. Converting between joules and watt-hours (1 Wh = 3600 J) is essential when comparing a battery rating to a measured power draw.
Example conversions
- 1 Wh = 3600 J — a small coin-cell energy budget.
- 18.5 Wh = 66,600 J — a typical laptop battery cell.
Frequently asked questions
How do I convert watt-hours to joules?
Multiply by 3600. 1 Wh is 3600 J.
How do I convert joules to watt-hours?
Divide by 3600. 7200 J is 2 Wh.
How do I convert kilowatt-hours to watt-hours?
Multiply by 1000. 0.5 kWh is 500 Wh.
Related converters
Energy is closely related to these quantities in everyday electronics work.