Battery Capacity Calculator

There is a limited number of molecules available to react in any charged battery. And, there is a limited amount of charge that a battery can move through a circuit before its energy runs out. Rather than measuring a battery’s capacity in electrons, we use the amp-hour. The amp-hour is a unit of charge, not current; one amp-hour is enough charge for a one-amp current that flows for one hour

Battery Life
Load Current (Consumption of Device)

Battery Capacity Rating


$$Q = I X t $$

Q is the charge in coulombs, I is the current in amps, and t is the time in seconds. 

The amp-hour — how much charge is stored in a battery — multiplied by the average battery voltage will provide an estimate of how many watt-hours a battery contains.

$$E = C X Vavg$$

E is energy stored in watt-hours, C is the capacity in amp-hours, and Vavg is the average voltage during the energy discharge.



This calculator computes the capacity-related properties of a battery. The above calculation shows how much battery capacity is required to run a certain device and how many watt-hours the battery holds.


Further Reading