Drywall Calculator

How to use this calculator

1. Measure room length, width and wall height.
2. Decide whether you are boarding the ceiling.
3. Count doors and windows to subtract typical opening sizes.
4. Pick the sheet size: longer sheets mean fewer joints but are heavier to handle.
5. Use the compound, tape and screw quantities as a starting estimate.

Method & assumptions

Walls = 2 × (Length + Width) × Height − openings
Sheets = (Walls + Ceiling) × (1 + waste %) ÷ sheet area, rounded up
Compound ≈ 0.67 kg/m² · tape ≈ 1.2 m/m² · screws ≈ 1 per sq ft of board (rules of thumb)

Sheet area

4 × 8 ft = 32 sq ft; 1200 × 2400 mm = 2.88 m²

Openings

20 sq ft per door, 15 sq ft per window

Assumptions & limits

• Single layer of board; fire-rated assemblies may require two layers.
• Finishing quantities are rules of thumb for a standard finish.
• Not a fire, acoustic or moisture specification — follow manufacturer and local code.

Rounding: purchase quantities are always rounded up to whole bags, boxes, sheets or bundles. See our methodology.

Worked examples

In depth: drywall planning notes

Choosing sheet sizes and orientation

Drywall sheets in North America are 4 ft wide and 8, 10, 12 or occasionally 14 ft long; plasterboard in the UK and Australia is commonly 1200 mm wide and 2400, 2700 or 3000 mm long. Longer sheets mean fewer joints to tape and sand, which saves time and gives a better finish, but they are heavy and need to get through doors and up stairs. Many installers hang sheets horizontally on walls so the tapered edges meet at a comfortable height and the joint lines are shorter.

Ceilings are usually done first and with the longest sheets you can manage, often with a drywall lift. Thickness also varies: ½ in (12.5 mm) for walls is standard, ⅝ in (15 mm) for ceilings with wider joist spacing and for fire-rated assemblies.

Finishing materials and waste

Our joint-compound, tape and screw figures are rules of thumb for a standard finish. As a rough guide, a typical room uses about one 62 lb (4.5-gallon) pail of ready-mixed compound per 450 sq ft of board (0.67 kg per m²), around 370 ft of tape per 1,000 sq ft, and roughly one screw per square foot. Manufacturer handbooks give exact rates for their systems, and Level 5 finishes or skim coats use far more compound.

Waste covers cut-outs for doors, windows and outlets and offcuts that cannot be reused. 10% is typical; rooms with many openings, sloped ceilings or stairs need 15%. Window and door openings are not deducted from sheet count by default because sheets are usually hung across openings and cut out.

Fire-rated, moisture-resistant and acoustic boards have specific uses. Where a wall or ceiling forms part of a fire separation, such as between a garage and a house, the board type and fixing pattern are set by code — follow the tested assembly.

Planning the hang

Before ordering, sketch each wall and decide where sheets will go. Avoid joints at the corners of door and window openings; run a sheet across the opening and cut it out, because joints that line up with the corners of openings tend to crack. Stagger butt joints on adjacent rows. Mark stud positions on the floor and ceiling so screws hit framing.

Tips & common mistakes

• Hang ceilings first, then walls, so wall sheets support the ceiling edges.
• Run sheets horizontally on walls to reduce linear feet of joints.
• Use moisture-resistant board in bathrooms and cement board behind tile in wet areas.

Sources

1. USG – Gypsum Construction Handbook — checked 2026-10; verify before launch
2. Gypsum Association – GA-216 application specification — checked 2026-10; verify before launch
3. British Gypsum – White Book — checked 2026-10; verify before launch

Default values (bag yields, coverage rates, densities) are typical figures from manufacturer literature. Always check the label on the product you buy.

Cite or embed this calculator

DIYCalcLab. “Drywall Calculator.” Oct 18, 2026. https://diycalclab.com/drywall/drywall-calculator/

An embeddable version for blogs and contractor sites is planned.