About this battery life calculator
Estimate how long a battery will last. Enter the capacity in mAh and the load current, or the active and sleep currents with the active duty cycle for low-power devices, to get the average current and runtime in hours, days, months or years.
How to use the Battery Life Calculator
- Enter the battery capacity.
- Enter active and sleep current and the active percentage.
- Set the usable capacity and read the runtime.
Example
2000 mAh, 20 mA active 1 %, 50 µA sleep, 85 % usable → ≈ 284 days
Frequently asked questions
Why use less than 100 % of the capacity?
Cut-off voltage, temperature, high peak currents, self-discharge and aging reduce the energy you can actually use.
Is my data safe?
Yes. The tool runs entirely in your browser using WebAssembly. Nothing you type or upload is sent to a server, logged or stored.
Is it free?
Yes, completely free with no sign-up, no limits and no watermarks. It also works offline once the page has loaded.