Home improvement

Drywall calculator

Sheets for walls and ceiling, with openings taken out.

Reviewed FreeNo sign-up≈ 2 minutes

Your inputs

Drywall calculator
The four sides added up. In an L-shaped room, go all the way round.
From the finished floor to the ceiling.
The size of the board you buy.
The size of the board you buy.
Doors and windows you are not building or covering.
Advanced options
Only needed if you include the ceiling.
Inside measurement, wall to wall.
%
Extra material for cuts, breakage and adjustments. Left blank we use 10.

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Your result will appear here

There is no figure yet: nothing is calculated until you ask for it.

  1. Enter your measurements.
  2. Check the units and the assumptions.
  3. Press Calculate, or load the example.

Rather see a worked case? Press “Load example” and change any value afterwards.

Next step

Insulation calculator

Insulation goes between the board and the wall, measured over the same area.

Open the calculator

Where each number comes from Conversion constants are exact; densities and coverage rates come from cited sources; everything else is an assumption you can change. Methodology · Sources and updates

How to use it

  1. Add up the room perimeter and measure the wall height.
  2. Enter the sheet size you will be using.
  3. Choose whether you are boarding one side or both.
  4. Tick the ceiling if you are boarding that too.

How it is calculated

Net area divided by sheet area, rounded up:

wall area = perimeter x height net area = walls + ceiling - openings sheets = ceiling(net area x (1 + waste) / (sheet width x height)) x sides

The 10 % waste covers off-cuts. In a room with many doors or windows it should go higher, because every opening produces pieces that rarely fit anywhere else.

The sides multiplier matters: a stud partition is boarded on both faces, so it needs twice the sheets of a dry lining fixed against an existing wall.

Worked example

A room with a 46 ft perimeter and an 8 ft ceiling, 4 x 8 ft sheets, one side, 10 % waste:

  • Wall area: 46 x 8 = 368 sq ft
  • With waste: 405 sq ft
  • Area per sheet: 4 x 8 = 32 sq ft
  • Sheets: 405 / 32 = 12.6 → 13 sheets

Good to know

  • Boards only. This excludes track, studs, screws, tape and joint compound. As a guide, studs are spaced every 16 or 24 inches.
  • 8 ft or 9 ft sheets. If your ceiling is 8 ft 6 in, an 8 ft sheet forces a strip on every wall. Measure before choosing the format.
  • Ceilings: more waste. Boarding a ceiling creates more off-cuts and more breakage when handling. Use 15 %.
  • Moisture-resistant board in bathrooms. The quantity maths is identical, only the board type changes.

Frequently asked questions

How many sheets of drywall do I need?

For a room with a 46 ft perimeter and an 8 ft ceiling, boarding one side with 4 x 8 ft sheets, you need 13 sheets including 10 % waste.

What size is a standard drywall sheet?

4 x 8 ft is the US standard, with 4 x 10 and 4 x 12 also common. In Europe the usual format is 1.20 x 2.50 m. Enter the format you are buying.

Does it count both sides of a partition?

Only if you choose the two-sides option. A stud partition is boarded on both faces; a dry lining against an existing wall only on one.

How much waste should I allow?

10 % for straight walls, 15 % for ceilings or rooms with many openings, where off-cuts are rarely reusable.

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Related guides

How many sheets of drywall do I need?Guide, with the calculator next to it.How to measure a room correctlyGuide, with the calculator next to it.