Drywall thickness by location — ½″ on walls, ⅝″ on ceilings

Hang ½″ board on the walls and ⅝″ on the ceiling — the thicker ceiling board resists sagging between 24″ o.c. joists and adds fire rating (IRC R702). Thickness also sets weight: ¼″≈38, ⅜″≈44, ½″≈54, ⅝″≈70 lb per 4×8 sheet.

What this diagram shows

A section comparing where each drywall thickness goes. Standard ½-inch board (about 54 pounds per 4×8 sheet) hangs on the wall studs. Ceilings use ⅝-inch board (about 70 pounds per sheet) because the extra thickness resists sagging between joists spaced 24 inches on center and adds fire resistance, which IRC R702 calls for. Thinner ¼-inch board (38 lb) is for curved surfaces and overlay, and ⅜-inch (44 lb) for overlaying existing walls. Thicker board weighs more, which drives the total material weight the calculator reports.