How to Calculate Battery Life in mAh

Most battery life spans are rated based on mAh (milliamp hours). Certain brands, such as Sony, use different protocols to rate the predicted life time of their batteries. In some cases, no life span is rated at all. In such cases, mathematical equations can be used to convert between the various electrical components -- such as current, resistance and voltage -- to come up with the actual lifespan of the battery. Most batteries will print some combination of the voltage, amperage, and wattage of the battery.

• 1

  Write down the number of watt hours and volts listed on the battery. It is useful to write "Wh =" then the number of watt hours then "V =" and the number of volts. This will help keep the notes clear.

• 2

  Multiply the number of watt hours by the number of volts. The product will be the number of Amp hours (Ah).

• 3

  Multiply the number of Amp hours by 1000 to get the number of mAh (milliamp hours).