"Electric bike battery capacity is most commonly calculated in Watt-hours (Wh). It's the same measure as your household electricity bill which is in Kilowatt-hours (kWh).

To calculate your electric bike battery capacity, you need to multiply the batteries Voltage (V) by it's Amp-hours (Ah).

For example lets take a 52 Volt electric bike battery with 20 Amp-Hours:

52 V x 20 Ah = 1040 Wh (Watt-hours)

This is referred to as the batteries nominal capacity and it is a simplification of the actual capacity. The actual battery capacity is slightly different and depends on a multitude of factors such as temperature, discharge rate, age, how high it is charged, but what it comes down to is actually measuring the batteries capacity by discharging the battery from fully charged to fully discharged in real life conditions."