Watt-Hours Calculator

About this calculator

Watt-hours (Wh) measure a quantity of energy — how much power delivered over how much time — calculated for a battery as Wh = Ah × V, multiplying its amp-hour capacity by its voltage. This is different from amp-hours alone, which measure charge, not energy; two batteries with the same amp-hour rating can store very different amounts of usable energy if their voltages differ, which is why watt-hours (or kilowatt-hours, Wh ÷ 1000) is the fairer way to compare battery capacity across different voltage systems.

Electricians, solar/off-grid system designers, and EV and power-bank shoppers use watt-hours to compare batteries of different chemistries and voltages on equal footing, to size a battery bank against expected daily energy consumption, and to check airline carry-on limits, which are typically expressed in watt-hours (commonly capped around 100 Wh without special approval). Enter the amp-hour capacity and voltage to find the energy in watt-hours.