Photographers Warehouse

AMP Hours or Watt Hours

Battery Cell Manufacturers rate their products in Amp Hours (Ah) because it is a term of measurement that identifies current (capacity). Most electric instruments are rated in Amps while light bulbs (lamps) are the only product rated in Watts.
Consequently, Watt has become a much easier term for the average consumer to relate. Because of this trend, video camera manufacturers have recently changed rating of cameras from Amp to Watt.

The accepted standards of the Electrotechnical Commissions of Technical Standards and the correct way to measure a battery's capacity is in Amp Hours (Ah).

To calculate a battery's capacity Amp Hours (Ah) or Watt Hours (Wh)

Wh: Amp x Volt = Watt
AH: Watt ÷ Volt = Amp

To calculate Running Times

Ah: Ah ÷Amps = Running Time
Wh: Wh ÷ Watt = Running Time