Hi there, thanks for your question! We'd be happy to assist! The Catalina Sectional is fantastic and is expertly built to last right here in the USA- great choice!

We'll answer your specific questions but, to start, here are some additional measurements and information for your reference:

Overall Dimensions: 86"w x 86"d x 27"h
Seat Height: 18"h | Arm Height: 27"h | Arm Width: 6"w | Seat Depth: 23"d | Pillow Height: 34"h

Seat Depth- The seat depth of the Catalina is listed at 23"d which is the measurement of the distance between the front of the seat cushion and where it meets the back cushion.

Back Cushion Dimensions- great question! The back cushion measurement isn't listed but, after a bit of quick deductive math ;) it looks like they are roughly 22.5"w x 16"h. The way this measurement was calculated was to divide the inner width of the sofa by the number of cushions to get the width measurement (22.5"w). Then, the height measurement is taken by subtracting the seat height (where the back cushion rests) from the overall "pillow height" (the height it reaches overall) to get a measurement of 16"w.

Hope that helps! If you have any follow up questions or thoughts, please don't hesitate to reply to this comment thread and we'd be happy to assist in any way we can!

-Apt2B Customer Care