What is the formula to convert battery Watts to Ah?

Name: Server Room Environments Ltd
Address: St. Andrews Business Centre, Bromfield Industrial Estate, Queen's Lane, Mold, UK, CH7 1XB
Telephone: +448000306838
Price range: ££ - £££££

Some batteries are sized in Watts and others in Ampere-hours (Ah). To convert Watts to Ah divide the Watt figure stated for the battery by the dc voltage of the battery. For example a 360W 12Vdc battery is a 30Ah battery.