Battery Life Calculator

Battery life calculator

Enter the battery capacity and the load’s power draw to estimate runtime.

Battery capacity

Ah mAh

Power consumption

Ampere (A) Milliampere (mA)

Calculate

How battery life is calculated

Battery life (in hours) = Battery capacity ÷ Power consumption

Battery capacity is the total charge a battery can store, expressed in milliampere-hours (mAh) or ampere-hours (Ah).

Power consumption is the rate at which the connected device draws current, expressed in milliamperes (mA) or amperes (A).

Unit conversion

Both values are converted to a common unit before the calculation runs:

• If battery capacity is entered in ampere-hours (Ah), it's converted to milliampere-hours by multiplying by 1,000.
• If power consumption is entered in amperes (A), it's converted to milliamperes by multiplying by 1,000.

Calculating battery life

Once both values are in the same unit, battery life is found by dividing battery capacity (in mAh) by power consumption (in mA). The result is the estimated runtime in hours.

Displaying the result

For readability, the result in hours can be converted into the most appropriate unit of time — seconds, minutes, days, weeks, months, or years — depending on its size, rather than showing a single large or fractional number of hours.

This calculation gives an estimate, not an exact figure. Actual battery life varies with temperature, battery age and condition, and how consistent the device's power draw is over time.