All Cabinets are in inches.
The standard Depth of Wall cabinets in 12″. Wall cabinets will have the following format: W2430. The W IDENTIFIES that it is a wall cabinet, 24 indicates the width of 24″ and 30 indicates the height of 30″.
Base cabinets Have a similar FORMAT, however, the height & depth are always a standard 34.5″ tall & depth of 24″. So, B15 would be a 15″ wide base cabinet.