Drywall Calculator
Wall, ceiling, and sheet estimator
Enter surfaces, openings, and drywall sheet size
Result
Calculation summary
Enter values to see the result
Drywall coverage preview
Room drywall coverage
How to use this calculator
- 1Choose a whole room, a single wall, or multiple walls and enter the measured dimensions.
- 2Include the room ceiling when needed, then add doors, windows, or custom openings to subtract.
- 3Select a standard drywall sheet or enter a custom size, choose a waste allowance, and calculate.
Formula
Sheets = ceil(((net wall area + ceiling area) × (1 + waste ÷ 100)) ÷ sheet area)
Door and window deductions apply only to wall area. The adjusted board area is divided by one sheet area and rounded up to a whole sheet.
Calculation steps
- Validate room, wall, opening, sheet-size, unit, and waste inputs.
- Convert dimensions to meters and calculate gross wall area.
- Subtract openings from wall area without allowing a negative wall result.
- Add the ceiling area when selected, then apply the waste allowance.
- Divide by the selected sheet area and round up to the next whole sheet.
Worked example
A 5 m × 4 m room with 2.8 m walls has 50.4 m² of wall area. With 10% waste and 1.2 m × 2.4 m sheets, the adjusted area is 55.44 m², requiring 20 sheets.
Assumptions
- Rooms are rectangular and use a uniform wall height.
- Walls, ceilings, doors, windows, and sheets are treated as rectangles.
- Door and window deductions apply to walls and never reduce ceiling area.
- The waste percentage is an area allowance and does not model the exact sheet layout or seam placement.
- Sheet counts are rounded up; local installation rules, fire ratings, thickness, and framing layout must be checked separately.
Sources
Frequently asked questions
How much extra drywall should I allow for waste?
Ten percent is a common planning allowance for straightforward rooms. Complex layouts, angled cuts, small sections, and inexperienced installation may require more.
Should I subtract doors and windows?
Yes for a closer material estimate. On small jobs, leaving minor openings in the total can also provide useful spare material.
Does the ceiling option subtract doors and windows?
No. Opening deductions are limited to the wall area, while the selected ceiling area is added separately.
Which drywall sheet size should I choose?
Use a size available from your supplier and suitable for access, framing layout, handling, and local installation requirements.
Does the estimate include screws, joint compound, or tape?
No. This version estimates drywall sheets and purchased board area only.