Laptop Battery Runtime Calculator
Estimate unplugged runtime using battery energy, health and average power draw.
iTechVora Tools
Laptop Battery Runtime Calculator
Estimate unplugged runtime using battery energy, health and average power draw.
Free · No signup · Calculations run in your browser
Ready to calculate
How to use
Enter values from your device specifications or measurements, then select Calculate. Defaults are editable examples. Copy result saves a text summary; Copy link shares your inputs. Reset restores the example.
Methodology
Usable Wh = new capacity Wh × health / 100 × (start charge − stop charge) / 100. Runtime hours = usable Wh / average battery watts.
Worked example
A 60 Wh battery at 90% health used from 100% to 10% supplies 48.6 Wh. At a steady 10 W draw, the estimate is 4.86 hours.
Limits and sources
Use average battery discharge power, not charger wattage or CPU TDP. Brightness, background tasks, temperature and load change runtime. If entering current full-charge capacity instead of new capacity, set health to 100% to avoid applying degradation twice.
Background reference: Official guidance. The source supports the background concepts; results use the formula above.
FAQ
Can two laptops with the same Wh have different runtime?
Yes. Their average power consumption can differ substantially, so capacity alone cannot predict runtime.
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Methodology version 1 · Updated October 11, 2026.