What TV size fits an 8-foot seat? The 30 to 40 degree range

How this is calculated

The 40 degree THX target is the wider of the two references. The 30 degree figure is the historical SMPTE EG 18-1994 geometry, and SMPTE withdrew that document in 2003, so the number works as a geometry reference only. From 8 feet, a TV with a diagonal of 59 inches fills 30 degrees, and one of 80 inches fills 40. Every diagonal between those two falls inside the band, which is why this seat has a range of sizes instead of one right answer.

Verdict

Pick a size from the band, then check the room. Measure from the front of the screen to your eyes in the spot where you'll sit. Across the retail sizes in range, the view runs from 33 to 39 degrees. An 85-inch TV fills 42 degrees from here, past the 40 degree target, so a seat farther back would bring it inside the target.