Drywall Needed Calculator

Drywall is sold in whole sheets, so the job is to add up every surface, take off the openings, divide by the sheet area and round up with a waste allowance.

Room lengthThe longer horizontal dimension of the room, in feet.Room widthThe shorter horizontal dimension, in feet.Wall heightFloor to ceiling height, in feet.Sheet sizeLonger sheets cover more and leave fewer seams to tape.Include the ceilingThe ceiling is usually the largest single surface in a room.OpeningsTotal area of doors, windows and anything not boarded, in square feet.Waste allowance(%)Ten percent suits a rectangular room, more for angled walls.

Sheets needed

Wall area: 448
Ceiling area: 192
Total surface: 640
Area after openings: 598
Sheets before waste: 19

Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.

The formula this calculator uses

sheets = ceil((wall area + ceiling area - openings) / sheet area x (1 + waste))

wall area: Perimeter times the wall height
ceiling area: Length times width of the room
sheet area: 32, 40 or 48 square feet depending on the sheet length
waste: Extra allowance for cuts around openings and corners

How to check the result by hand

1
Work out the wall area from the perimeter
The perimeter of a 16 by 12 foot room is 56 feet. At a height of 8 feet that is 448 square feet of wall.
2
Add the ceiling
The ceiling is 16 by 12, which is 192 square feet. Include it only if you are boarding the ceiling as well as the walls.
3
Subtract the openings
Two windows and a door remove 42 square feet, leaving 598 square feet of surface that actually needs boarding.
4
Divide by the sheet area and add waste
598 over 32 is 18.6875 sheets, and ten percent waste takes that to 20.5563, so 21 sheets of 4 by 8 go on the order.

For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Drywall Needed page.