Battery Runtime Calculator
Estimate how long a device will run on battery, based on its capacity, nominal voltage, average power consumption, and a realistic energy-loss margin. Fully local calculation, in your browser.
How It Works
The calculation first converts battery capacity and device consumption into a common energy unit (watt-hours), based on the specified nominal voltage, then divides the available energy by the power consumed to get a duration in hours. An efficiency factor is applied to account for unavoidable losses (heat, voltage regulation, battery aging).
Why apply an efficiency factor below 100%?
No battery delivers 100% of its theoretical energy: part is lost as heat, in regulation circuits, or due to cell aging. A value between 80 and 90% is a realistic order of magnitude for most modern lithium-ion batteries, but you can adjust it based on real-world observations.
Does the result apply to any device?
The calculation principle (available energy divided by power consumption) applies to any battery-powered device, whether it's a smartphone, an e-bike, or a cordless tool, provided you enter a realistic average consumption: a device with highly variable usage (screen on or off, workload, etc.) will have a different average consumption depending on real usage.
The calculation runs entirely in your browser, with no data sent to a server.