Wh Runtime Calculator

Estimate battery runtime from capacity and load. The calculator also shows energy after reserve and conversion loss.

Enter capacity in watt-hours, load in watts, duty cycle, reserve, efficiency, and idle draw.

The calculator subtracts reserve from capacity. It divides average load by efficiency and adds idle draw.

It divides the remaining capacity by that load to estimate runtime. The tool rounds the result to one decimal place.

The formula comes from the site's runtime calculator. Equipment inputs are assumptions that you can change.

Estimate only; check the maker's manual. The estimate does not check surge load or electrical safety.

Capacity examples from the catalog

These examples use capacity from the product title and the tool's starting assumptions.

Each example uses a 48 W load, 32% duty cycle, 10% reserve, 85% efficiency, and 8.5 W idle draw.