Free drywall calculator.
This free drywall calculator returns the square footage and sheet count for a rectangular room, subtracting doors, windows, and other openings. Pick a sheet size (4×8, 4×10, or 4×12 ft) and a waste percentage; the result rounds up to whole sheets for ordering. Imperial or Metric.
Drywall needed
Want this measured straight from your PDF instead? BidScreen XL adds the same math to Microsoft Excel — trace the drawing, the quantity lands as a live cell.
Perimeter × height, minus openings.
The wall area of a rectangular room is the perimeter times the ceiling height: 2 × (length + width) × height. For a 12 × 14 ft room with 8 ft ceilings, that's 2 × (12 + 14) × 8 = 416 ft². Add the ceiling area (length × width) if you're hanging board on the ceiling too.
Subtract opening areas — each door, window, and pass-through. Standard interior doors are 3 × 6'8" ≈ 20 ft². Standard windows vary widely; measure rough opening, not visible glass.
The remainder is the net board area. Add 10-15% waste (the calculator does this), then divide by the sheet area to get the sheet count. The result rounds up because suppliers don't sell partial sheets.
Frequently asked
How do I figure out drywall for a room?
Multiply the room's wall perimeter by the ceiling height — that's the gross wall area. Subtract the area of every door and window (height × width × count). Add the ceiling area (length × width) if you're drywalling the ceiling too. Add 10-15% for waste and round up to whole sheets.
What sheet size should I use?
4 × 8 ft sheets (32 ft²) are the standard residential size — easy to handle, fits in pickup trucks. 4 × 12 ft sheets (48 ft²) reduce seams and labor on commercial work but need two people to handle. 4 × 10 ft is the middle ground for tall residential walls. Pick what your installer prefers.
How much waste should I add?
10% is the typical default. 12-15% for rooms with many openings, complex cutouts, vaulted ceilings, or short cuts. Larger sheets need less waste because there are fewer cuts; smaller sheets need more.
Should I include the ceiling?
Toggle the ceiling option on if you're drywalling the ceiling. Ceiling area = length × width. The calculator adds it to the wall area before subtracting openings.
How do I order drywall from this number?
The sheet count is rounded up to the next whole sheet. Suppliers sell in full sheets only. A typical hardware store keeps 4×8 in stock; specialty sizes may need a special order. For commercial drywall (Type X fire-rated, moisture-resistant green board), specify the type when ordering.
BidScreen XL traces drywall from the plan.
For multi-room jobs, trace each room's walls and ceiling on the PDF and BidScreen XL pulls the live square footage straight into your Excel estimating workbook — already adjusted for openings and ready for a sheet-count formula.