Drywall Calculator

This is an estimate, not professional advice. Check your inputs and verify the result against your plans and local building code before you build or order. See terms and disclaimer.

How this calculator works

Enter your dimensions and the result updates instantly. A waste allowance is included so you order slightly over rather than running short mid-pour, and ready-mix is rounded up to the nearest quarter yard, which is how it is sold.

Worked example

A 12 ft × 12 ft room with an 8 ft wall height, walls plus ceiling, and a 10% waste allowance. Inputs: Room length 12 ft, Room width 12 ft, Wall height 8 ft, Include ceiling 1, Sheet size 32, Openings (doors, windows) 0 ft², Waste allowance 10 %. Result: 19 .

Drywall sheets for common room sizes

Walls plus ceiling, 8 ft height, 4 x 8 ft sheets and a 10% waste allowance. Tap a size to load it in the calculator above.

Method & assumptions

We work out the surface you actually need to cover, not just the floor plan. Wall area comes from the room perimeter times the wall height, and you can add the ceiling for a full gut-and-redrywall job or leave it out for a walls-only patch or remodel. Subtract the combined area of any doors and windows, add your waste allowance for cuts and damaged boards, then divide by the coverage of the sheet size you picked and round up, because you cannot buy a partial sheet.

Screw count uses the widely cited rule of 32 fasteners per standard 4 x 8 ft sheet of 1/2 in drywall, which comes from roughly 16 in field spacing and 8 in edge spacing along the framing, the maximum spacing allowed by the International Residential Code for that thickness. Ceilings, thicker 5/8 in board or 24 in on-center framing need tighter spacing and more screws, so treat this as a solid baseline and adjust up for those cases.

Joint compound is estimated at about 10 gallons per 1,000 square feet of board, the coverage USG publishes for its Sheetrock Brand All Purpose Joint Compound across a standard three-coat, Level 4 finish (tape coat, fill coat and finish coat). Install methods follow the Gypsum Association's GA-216 standard for application and finishing of gypsum panel products, the specification referenced by the International Building Code. Heavier textures, a Level 5 finish or a lot of butt joints will use more mud than this baseline. For the raw floor or wall area on its own, use our square footage calculator, and for the finished floor covering see the flooring calculator.

Pro tips and common mistakes

• Round dimensions up before you multiply. Measure to the widest points of each wall and round up, so 11 ft 6 in becomes 12 ft. It is cheaper to have one extra sheet than to run short mid-job.
• Match sheet size to the wall. Longer 12 ft sheets mean fewer horizontal seams on tall or long walls, which means less taping and a flatter finish. They are heavier and need two people to hang safely.
• Ceilings need closer screw spacing. Gravity works against ceiling board, so tighten field spacing to about 12 in instead of 16 in. Budget more screws per sheet on the ceiling than the walls in the total above.
• Buy one extra sheet. A single spare sheet covers accidental damage and small mistakes without a separate trip to the store, and drywall does not go bad sitting in the garage.
• Stagger the joints. Offset vertical seams between rows so they do not line up, and never let four corners meet at one point. Staggered joints are far less likely to crack along the seam later.

Frequently asked questions

References

• Drywall (Wikipedia)
• Gypsum Association, GA-216 Application and Finishing of Gypsum Panel Products
• USG Sheetrock Brand All Purpose Joint Compound, coverage submittal sheet

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