🧱 Drywall Sheet Calculator

Enter your total wall or ceiling area and sheet size to find out how many drywall sheets to buy.

Total Wall/Ceiling Area (sq ft)

Sheet Size

Waste/Cuts Allowance (%)

How the sheet count is worked out

The waste allowance is applied to your area first, and the padded area is then divided by the coverage of one sheet and rounded up. A 4 x 8 board is 32 sq ft and a 4 x 12 board is 48 sq ft.

padded area = area x (1 + waste% / 100)
sheets      = ceiling(padded area / sheet coverage)

The default 480 sq ft is the four walls of a 14 x 16 ft room at an 8 ft ceiling: a 60 ft perimeter times 8 ft. At 10% waste that becomes 528 sq ft, which is 17 sheets of 4 x 8.

Getting the area right, and the waste with it

Walls are the room perimeter times the ceiling height.
Ceilings are length times width, added on top.
Do not deduct doors and windows unless they are unusually large. Board is hung straight over an opening and cut out afterwards, and the piece that comes out is mostly scrap.

10% is the working figure for a plain rectangular room. Push it to 15% when there are several openings, a stairwell, sloped ceilings or short returns, because every one of those turns a full sheet into a cut piece with an awkward leftover. A cut edge also has no factory taper, so offcuts are worth less than their square footage suggests - a butt joint between two cut edges is the hardest thing in the room to hide.

Sheet thickness is not a preference. Garage ceilings under living space, party walls and attached-garage walls commonly require 5/8 in fire-rated board, and ceilings at 24 in framing centres need 5/8 in to avoid sagging. Your local building rules decide this, not the sheet count, and the count does not change with thickness anyway.

Frequently asked questions

How many sheets of drywall for a 12x12 room?

Walls at an 8 ft ceiling are 384 sq ft and the ceiling adds 144, so 528 sq ft in total. With 10% waste that is 19 sheets of 4 x 8, or 13 sheets of 4 x 12.

Should I use 4x8 or 4x12 drywall sheets?

4 x 12 if you can carry it and get it through the door. Longer boards span a standard wall in one piece, which removes butt joints entirely and cuts the taping down sharply. The trade-off is weight: a 1/2 in 4 x 12 sheet is around 80 lb and genuinely needs two people, especially overhead.

How much drywall waste should I allow?

10% for simple rooms, 15% once there are many windows, doors, angles or a stairwell. The allowance covers cut-outs, damaged corners and offcuts too small to be worth hanging - it is not a safety margin you get to keep.