How the math works
Wall area = perimeter × ceiling height.Ceiling area = length × width.Add 10% waste.Divide by 32 (4x8) or 48 (4x12) and round up.
Trade pro tips
- Order 4x12 sheets for long walls to cut down on butt joints.
- Check that sheets fit up the stairs before ordering 12-footers.
Frequently asked questions
How do I calculate how much drywall I need?
Add the wall area (perimeter × height) and ceiling area, add 10% waste, and divide by 32 for 4x8 sheets or 48 for 4x12.
How many square feet is a sheet of drywall?
4x8 = 32 sq ft, 4x10 = 40 sq ft, 4x12 = 48 sq ft.
Should I subtract windows and doors?
For small rooms, no — the offcuts are rarely reusable. For openings over about 50 sq ft, subtract them.
How much joint compound per sheet?
Roughly 1 gallon of all-purpose mud per 100 sq ft for three coats — a 4.5 gal bucket covers about 450 sq ft.