Skip to content
Yardwork

Drywall Calculator

Free drywall calculator: enter the room size or total area, openings, and sheet size to see how many sheets of drywall (sheetrock) to buy.

  • Free, no signup
  • Formula shown
  • Rounds up to whole units
  • Updated October 2026

Common rooms (8 ft walls)

Room
Units
Measure by
Include the ceiling?

Doors, windows, large openings.

For cuts and breakage.

Sheets

4 × 8 ft sheets · 10% allowance

19sheets

Area to cover

534 sq ft

after openings

Per sheet

32 sq ft

18.36 sheets exact

Wall area
416 sq ft
Ceiling area
168 sq ft
With allowance
587.4 sq ft

Area-based estimate. It does not plan sheet layout or guarantee that offcuts can be reused.

14 × 8 ft wall, 4 × 8 ft sheets
One wall with sheets hung horizontally (seams shown)

AnswerCovering 534 sq ft after openings, plus a 10% allowance, takes 18.36 sheets of 4 × 8 ft drywall, so buy 19 sheets.

How to use this drywall calculator

  1. Choose feet or meters, then enter the room's length, width, and wall height, or switch to Total area.
  2. Choose whether to include the ceiling.
  3. Add up the area of doors, windows, and other openings (width × height each) and enter it.
  4. Pick the sheet size you'll buy, or enter a custom size, for example for metric sheets.
  5. Set a waste allowance for cuts, breakage, and pieces you can't reuse.

How to calculate drywall: the formula, shown

Wall area is the room's perimeter times the wall height: 2 × (length + width) × height. Add the ceiling (length × width) if you're covering it, subtract openings, and add an allowance. Divide by the area of one sheet and round up to a whole sheet.

Default example. A 14 × 12 ft room with 8 ft walls, ceiling included, 50 ft² of openings, 4 × 8 ft sheets, and a 10% allowance. Change the inputs above and the result panel recalculates; this worked example always shows the default.

Default example arithmetic
Walls       = 2 × (14 + 12) × 8 = 416 ft²
Ceiling     = 14 × 12 = 168 ft²
Net area    = 584 − 50 = 534 ft²
Allowance   = 534 × (1 + 10/100) = 587.4 ft²
Sheet area  = 4 ft × 8 ft = 32 ft²
Sheets      = 587.4 ÷ 32 = 18.356 → 19 sheets

Drywall sheets for common room sizes

Drywall sheets for common rooms with 8 ft walls, computed with the same formula as the calculator. No openings are deducted, and a 10% allowance is included. Subtract doors and windows in the calculator for your room.

Drywall sheets for common room sizes
RoomWalls: 4×8Walls: 4×12Walls + ceiling: 4×8Walls + ceiling: 4×12
10 × 10 ft1181510
10 × 12 ft1391711
12 × 12 ft1491913
14 × 12 ft15102114
16 × 14 ft17112517
20 × 16 ft20143121
20 × 20 ft22153624

How many sheets of drywall do I need?

For the default room, buy 19 sheets of 4 × 8 ft drywall.

  • Area, not layout: this is an area-based estimate. It doesn't plan where seams fall, and it doesn't guarantee that offcuts can be reused. Rooms with many openings, angles, or short wall sections may need more. Raise the allowance, or lay out the sheets on a sketch.
  • Sheet length: longer sheets mean fewer joints, but they are heavier and harder to carry. USG lists its UltraLight panels in 4 ft or 54 in widths and 8–16 ft lengths. Check what your supplier stocks.
  • Panel type: ceilings, wet areas, and fire-rated assemblies may call for specific panels and thicknesses. Follow your plans and local code. This calculator counts sheets only.
  • Finishing: joint tape, compound, screws, and corner bead are separate items.

Tips for estimating drywall

  • Measure each wall separately when the room isn't a simple rectangle, and use Total area with the sum.
  • Gable-end walls are triangles above a rectangle. See measuring irregular areas.
  • Buy one or two extra sheets for breakage if the store is far away. It's cheaper than a second trip.
  • Painting afterwards? Use the same wall area in the paint calculator.

Drywall calculator FAQ

How many sheets of drywall do I need?

Add up the wall area (perimeter × height) and the ceiling area if you're covering it. Subtract openings, add a waste allowance, and divide by the area of one sheet: 32 sq ft for a 4 × 8 sheet. Round up to a whole sheet.

How many sheets of drywall for a 12 x 14 room?

With 8 ft walls and the ceiling, the room has 584 sq ft. Subtract 50 sq ft for openings, add a 10% allowance, and divide by 32 sq ft per 4 × 8 sheet. That gives 18.36, so buy 19 sheets.

How many square feet are in a sheet of drywall?

Multiply width by length. A 4 × 8 ft sheet is 32 sq ft, 4 × 10 is 40, 4 × 12 is 48, and a 54 in × 12 ft sheet is 54 sq ft.

What size do drywall sheets come in?

Sizes vary by product. USG lists its Sheetrock UltraLight 1/2 in panels in 4 ft or 54 in widths and lengths from 8 to 16 ft, with other sizes by special order. Check what your supplier stocks.

How much extra drywall should I buy?

It depends on the room. Simple rectangular rooms waste less than rooms with many openings, angles, or short walls. The calculator defaults to 10% as an adjustable example. Raise it for complicated rooms.

Should I subtract doors and windows?

Usually yes, for large openings like doors and windows. Small openings such as outlets are normally cut out of full sheets and don't reduce the sheet count.

Does this calculator plan the sheet layout?

No. It is an area-based estimate. It doesn't place seams or guarantee that offcuts can be reused. For an exact count, sketch each wall and lay out the sheets.

Can I calculate metric drywall sheets?

Yes. Switch to meters, enter the room or area in metric, and choose Custom size to enter your sheet's width and length in meters.

Calculators

  • Paint Calculator — Gallons or liters of paint for your walls and number of coats, using the coverage printed on your paint's label.
  • Deck Calculator — Decking board count from deck size, actual board width, gap, and board length, with the cutting assumptions shown.
  • Roof Pitch Calculator — Pitch as x/12, roof angle in degrees, slope percentage, and the sloped length for a given horizontal run.

Guides

Sources