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Drywall Calculator

Room size in, sheets of drywall out, plus screws, tape and mud for the job.

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Drywall needed

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Hang the ceiling first, then the top row of the walls

Ceiling sheets go up before the walls so the wall board can support their edges. On the walls, hang the top sheet tight to the ceiling and let any gap fall at the floor, where the baseboard hides it. You get a cleaner ceiling line and less taping overhead.

How the drywall calculator works

Wall area for a rectangular room is 2 × (length + width) × wall height. The ceiling, if you include it, adds length × width. From that the calculator subtracts about 21 sq ft for each standard 3 × 7 ft door and 15 sq ft for each 3 × 5 ft window.

Sheets needed equal area × (1 + waste %) ÷ sheet area, rounded up. A 10% allowance covers cutoffs around openings, outlet boxes and inside corners. Longer 4 × 12 sheets mean fewer butt joints to tape, which is why pros prefer them on walls where they can get them into the room.

The supply lines use common trade rules of thumb: about one screw per square foot of board at 16 in. framing, about 370 ft of paper tape per 1,000 sq ft, and about 10 gallons of ready-mixed joint compound per 1,000 sq ft for taping plus two finish coats, which is the figure USG publishes for its Sheetrock All Purpose compound.

Where these numbers come from

The formulas and default values in this calculator are based on:

  • USG Sheetrock All Purpose Joint Compound submittal (approx. 10 gal per 1,000 sq ft of gypsum panels)
  • USG Gypsum Construction Handbook fastening and taping guidance

These are planning estimates. Check product labels, your local building code, and a licensed contractor before you buy materials or build.

Frequently asked questions

Should I subtract doors and windows from my drywall estimate?

Most pros subtract them, then add back 10% or so for waste, which is what this calculator does. On a small room with many openings, some installers skip the subtraction entirely, because the pieces cut out of openings are often too awkward to reuse.

Is 1/2 inch or 5/8 inch drywall right for my project?

Half-inch board is standard for walls in most houses. Five-eighths is common on ceilings with framing 24 in. on center because it sags less, and Type X 5/8 in. is what codes require on garage walls and ceilings shared with living space. The sheet count is the same either way; only weight and price change.

Why is my sheet count higher than area divided by 32?

The waste allowance and rounding both push the number up. You also can't use a fraction of a sheet efficiently across different walls, so an extra sheet or two on the order is normal and cheaper than a second trip.

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