Battery Life Calculator
Estimate how long a battery will last between charges. Enter the battery capacity in mAh and pick how heavily you use the device, and the calculator divides the capacity by an estimated drain rate to show the approximate runtime in hours.
Formula
Runtime (hours) = Battery Capacity (mAh) ÷ Drain Rate (mA/hr)
- Runtime in hours = battery capacity (mAh) ÷ average current draw (mA).
- Usage presets estimate the average draw: light/standby ≈ 50 mA, normal/mixed ≈ 200 mA, heavy/constant use ≈ 500 mA.
- Real-world current varies with screen brightness, signal strength, temperature and the apps running, so treat this as a ballpark.
- Battery capacity also fades as a battery ages, so an older device will run for less time than its rated mAh suggests.
5000 mAh battery, normal usage
Inputs
- Battery Capacity (mAh): 5000
- Usage Type: normal
Normal usage draws about 200 mA. Runtime ≈ 5000 ÷ 200 = 25 hours of mixed use on a full charge.
Frequently asked questions
How is battery life estimated?
By dividing the battery capacity in mAh by an estimated average current draw in mA. The usage presets supply a typical draw for light, normal and heavy use.
Why is my real battery life different?
Actual current draw changes constantly with brightness, signal, temperature and background apps, and batteries lose capacity as they age. This is a rough estimate, not an exact figure.
What does mAh mean?
Milliamp-hours measure how much charge a battery holds. A 5000 mAh battery can in theory supply 5000 mA for one hour, or 500 mA for ten hours.
How can I make my battery last longer?
Lower the screen brightness, close power-hungry apps, turn off unused radios (GPS, Bluetooth) and avoid extreme temperatures — all of these reduce the average current draw.