Drywall & Plasterboard Calculator

How many sheets of drywall or plasterboard you need for walls and ceilings: 4 × 8, 4 × 12 ft or 2400 × 1200 mm boards, with openings taken off.

Drywall (plasterboard in the UK and Australia) is sold in sheets, so you need the area of walls and ceilings divided by the area of a sheet, plus extra for offcuts. A 12 × 10 ft room with 8 ft walls has 352 ft² of wall; with a door and window taken off and the ceiling added, that's about 440 ft², which with 10% extra is 16 sheets of 4 × 8 ft. Enter rooms or individual walls, choose your sheet size (4 × 8, 4 × 10 and 4 × 12 ft in the US; 2400 × 1200 mm and smaller boards in the UK; 2400 to 4800 mm long boards in Australia) and the calculator counts the sheets, with the working shown.

Units
Bag sizes
Measure by
Room
ft
ft
ft
Feet and inches work too: type 12'6 or 12.5.
Doors and windows to leave out
ft
ft
ft
ft
%
Sheets
16

4 × 8 ft

Area to cover
440 ft²

incl. 120 ft² of ceiling

Sheet area
32 ft²

15.13 sheets before rounding

How it was worked out
  1. Walls: 2 × (12 + 10 ft) = 44 ft around × 8 ft high = 352 ft²
  2. Ceiling: 12 × 10 ft = 120 ft²
  3. Less 1 door (20 ft²) and 1 window (12 ft²) = −32 ft²
  4. Area to cover: 440 ft²
  5. Plus 10% for offcuts = 484 ft²
  6. 484 ft² ÷ 32 ft² per 4 × 8 ft sheet = 15.13, rounded up to 16 sheets

This counts sheets by area. Long walls and tall ceilings can need more if the sheets don't divide neatly, so check your layout, especially with long sheets.

Common use cases

  • Order drywall or plasterboard for a new room, basement or garage
  • Board a ceiling as well as the walls
  • Compare how many 4 × 8 ft or 4 × 12 ft sheets a room needs
  • Patch or reboard a single wall

How to use

  1. Choose your units and which country's sheet sizes you want.
  2. Enter each room's length, width and wall height, or switch to Wall for single walls.
  3. Enter the doors and windows, and tick Include ceilings if you're boarding them.
  4. Choose a sheet size and the extra for offcuts, then read the number of sheets.

FAQ

How many sheets of drywall do I need for a room?

Add up the wall area (perimeter × height), add the ceiling if you're boarding it, take off doors and windows, add 10 to 15% for offcuts and divide by the sheet area: 32 ft² for a 4 × 8 sheet, 48 ft² for a 4 × 12, or 2.88 m² for a 2400 × 1200 mm board.

Should I use longer sheets?

Longer sheets mean fewer joints to tape and finish, which saves time and gives a better result, but they're heavier and harder to get into the room. Many installers hang 12 ft sheets horizontally on walls where they'll fit.

Do I subtract windows and doors?

Most people subtract doors and large windows and ignore small openings, since the offcuts from small openings are rarely usable anyway. The extra allowance covers the difference.

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