Other Calculators

Battery Capacity (Energy) Calculator

Convert a battery's capacity (mAh) and voltage into total stored energy (watt-hours), and estimate runtime for a given power draw.

Stored energy —

Estimated runtime at this power draw —

About the Battery Capacity (Energy) Calculator

A battery's mAh rating only tells part of the story — its actual energy content also depends on voltage. Multiplying the two together converts capacity into watt-hours (Wh), a voltage-independent measure of stored energy used to compare batteries of different chemistries and voltages.

Formula: Energy (Wh) = (Capacity in mAh ÷ 1000) × Voltage. Runtime (hours) = Energy (Wh) ÷ Power Draw (W)

This is why a 10,000mAh USB power bank (usually around 3.7V, roughly 37Wh) stores less energy than its raw mAh number suggests compared to a 12V car battery of the same mAh rating.