Dining benches vary considerably in depth. A no-frills, Amish-style bench might measure just 12 inches, while an upholstered, built-in dining bench with storage underneath measures a generous 23 inches. Features such as built-in storage require a design with more depth.
Standard stock dining bench cushions typically measure 16 inches in depth. You can purchase custom-made cushions in any size you like. Yet, to keep costs down, consider a dining bench depth between 16 and 18 inches, which will accommodate many stock cushions. Back rest cushions require a bench with a deeper seat.
Regarding seat depth, The BIFMA states that users should be able to sit in a chair without undue pressure against the backs of their knees. Think about the size of the individuals using the bench. Tall individuals may prefer a deeper bench, while petite individuals will find a narrower depth more comfortable.