Home improvement planning
Drywall Calculator
Plan drywall for a rectangular room without guesswork. Choose walls, ceiling, or both; subtract doors and windows; then estimate full sheets and material cost with a waste allowance.
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Your project summary
Results
Enter your measurements to see an estimate.
A little planning goes a long way
How It Works
Choose the surfaces
Select walls, the ceiling, or both, then enter the room dimensions in feet or meters.
Match your sheets
Enter the length and width of the drywall sheets available for your project, plus the average door and window sizes.
Plan the purchase
We deduct wall openings, add waste, divide by sheet coverage, and round up to full sheets.
Formula
- Wall Area
- 2 × (room length + room width) × wall height
- Opening Area
- door area + window area
- Drywall Area
- selected wall area − openings + selected ceiling area
- Area With Waste
- drywall area × (1 + waste ÷ 100)
- Sheets Needed
- Round up (area with waste ÷ area per sheet)
- Estimated Cost
- sheets needed × price per sheet
Example Calculation
A 12 × 10 ft room with 8 ft walls and ceiling, one 3 × 7 ft door, two 3 × 4 ft windows, 4 × 8 ft sheets, 10% waste, and a $15 sheet price.
- Walls: 2 × (12 + 10) × 8 = 352 sq ft.
- Openings: (1 × 3 × 7) + (2 × 3 × 4) = 45 sq ft.
- Walls plus ceiling: 352 − 45 + 120 = 427 sq ft.
- With waste: 427 × 1.10 = 469.7 sq ft.
- Each sheet covers 32 sq ft; round the area-with-waste estimate up to 15 sheets.
- 15 × $15 = $225.00 in drywall sheets.
Buy 15 sheets. The drywall estimate is $225.00 before tax and installation supplies.
FAQ
How much drywall waste should I allow?
The editable default is 10%. Simple rooms with a planned layout may need less; many corners, small sections, damaged sheets, or difficult access may require more.
Should I subtract doors and windows?
This calculator deducts them when walls are selected. For small openings, some installers leave them in the estimate because offcuts may not fit elsewhere; raise the waste allowance if your layout produces unusable pieces.
Which drywall sheet size should I use?
Enter the exact sheet length and width you expect to buy. Larger sheets can reduce seams but are heavier and may be difficult to move into the room. Confirm available sizes, thickness, and board type with your supplier.
Why can an area estimate differ from a sheet layout?
Area division assumes offcuts can be reused efficiently. Real layouts depend on framing, sheet orientation, seam placement, openings, and handling. The waste allowance adds a planning margin but does not replace a panel layout.
Does the cost include finishing materials or labor?
No. The estimate prices full drywall sheets only. Tape, compound, fasteners, corner bead, tools, delivery, labor, and tax are excluded.