Battery Runtime Calculator

Use nominal battery energy and a steady load to estimate runtime; real batteries can differ with load, temperature, age, and protection limits.

Capacity

Capacity unit

Nominal voltage (V)

Steady load

Load unit

Conversion efficiency (%)

Usable capacity (%)

—Idealized runtime estimate

—Nominal energy

—Usable after factors

—Load power

—Minutes

This is an energy-balance estimate, not a battery-management-system or safety calculator. Actual runtime can change substantially with battery chemistry, discharge rate, temperature, aging, cutoff voltage, and device behavior.

How to use this Battery Runtime Calculator

Estimate idealized battery runtime from capacity, voltage, load, efficiency, and usable fraction. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.