Watt Hour Calculator

Watt hours measure an amount of energy: one watt held for one hour. Enter a power draw and a time, or a battery's capacity and its nominal voltage, and the tool returns the energy in watt hours, kilowatt hours and joules. A third action runs the same arithmetic backwards, turning stored watt hours and a load into a runtime, with an allowance for the losses in a power bank or an inverter. Milliamp hours on their own are a charge rather than an energy, which is why the voltage has to be asked for.