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How to Calculate Laptop Battery Run Time


You can determine how long your battery will run by dividing the battery capacity from the power consumption of your laptop. To do this you need to know how much energy your laptop uses (measured in watts) and the total power capacity your laptop battery has (measured in milli-amp hours or watt-hours).


Calculate Watt-Hours
Whr = Volts x mAh / 1000

Example:
14.8 Volts x 4060mAh / 1000 = 60.09 Watt-Hours (rounded up)

Calculate Milli-Amp Hours
mAh = Whr x 1000 / Volts

Example: 60.09 x 1000 / 14.8 = 4060 mAH (rounded down)


Calculate Battery Life
Run Time (Hours) = Whr / Watts

Example: 60.09 Whr / 20 Watts = 3.004 Hours

If your battery is rated 60.09 Whr and your laptop is rated 20 watts your battery run time will be:
3.004 hours (60.09 Whr / 20.0 Watts)

Will a higher mAh battery rating negatively affect my laptop?
No. A battery with a higher mAh rating will not damage your laptop or power charger. It just means the battery has will store more energy inside.