Battery Life Calculator

What this tool does

Dividing capacity by current gives a theoretical runtime that real batteries never quite reach, so an efficiency factor is included: 80–90 % is a realistic starting point for most chemistries. Cold temperatures, high discharge rates and ageing all reduce it further.

Formula

t = C × η ÷ I

Variables

Worked example

Limitations

• The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
• The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.