Reference Designer Calculators
Battery Life Calculator
If the capacity of a Battery is defined in terms of Watt Hour, you will need to know the voltage of the battery and the current drawn to be able to calculate the life of a battery. Watt itself is defined as Ampere X Voltage. So if a 5 Volt battery has 20 Watt Hour rating, and, it draws 2 Amp current, then the Watt delivered by Battery = 10 Watts ( 5 Volts x 2 Ampere). The battery will last 2 hours. The calculator will calculate the battery life if the Watt Hour and the battery voltage is known.
Here is the formula
Battery Life = Watt Hours / ( Voltage x Current in Ampere)
You may also like to check Watt Hour Vs Ampere Hour if the battery capacity has been defined as Watt Hour.