Laptop Battery Life Calculator
A rough guide to how long a laptop runs on one full charge. Battery size and average power draw decide most of the answer, and real use can change it a lot.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Usable energy is the battery size times the share of capacity left, since batteries hold less as they age. Dividing that energy by the average power draw gives the run time, shown as hours and minutes.
Average draw depends on screen brightness, the work you do and the chip inside. Light web use draws far less than video or games, so pick a draw that matches how you use the machine.
Worked example
A 60 Wh battery with 90% of its original capacity left, running at an average draw of 20 W, lasts about 2 h 42 min on one charge.
Questions
Why does my laptop last less than this shows?
Real use changes the draw from minute to minute, and high brightness or a warm room push it up. An older battery also holds less than it did when new.
Where do I find the battery size?
Many makers list it in watt-hours, Wh, on the spec page for the model. Enter that figure as the battery size.
How do I get a better average draw?
A battery report from your system can show how the charge fell over a normal day. An average over a full day is more useful than a single reading.
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