How can batteries with same voltge rated with Wh and mAh be compared?

watt = amp * volt

watt hour capacity = amp hour capacity * voltage

Calculate capacity in watt hour for the one which gives you mAh capacity with the following (dividing by 1000 to convert mA to A):

Wh capacity = (mAh capacity / 1000 ) * voltage

- Neeraj Sharma