Drywall Calculator
Sheets Needed14
Total Area384 sq ft
Estimating drywall before a project keeps you from making extra hardware-store runs or over-buying sheets that warp in the garage. This calculator totals your wall area, subtracts the square footage of doors and windows, adds a 10% waste allowance for cuts and breakage, and divides by the area of a standard 4x8 sheet (32 sq ft) to tell you how many sheets to buy.
Formula
sheets = ⌈((L × H × walls − openings) × 1.1) ÷ 32⌉
- L
- Length of one wall in feet
- H
- Height of one wall in feet
- walls
- Number of walls of that size
- openings
- Total area of doors and windows in sq ft to subtract
- 1.1
- 10% waste factor; 32 = area of a 4x8 sheet in sq ft
How it works
- Enter the length and height of a typical wall, plus the number of walls of that size — the tool multiplies them to get gross wall area.
- Enter the total square footage of openings (doors and windows) to subtract; this is a combined area, not a per-opening count.
- The net area is multiplied by a 1.1 waste factor, divided by 32 sq ft per 4x8 sheet, and rounded up to the next whole sheet.
Worked example
A room with four 12 ft × 8 ft walls and 21 sq ft of door and window openings.
- Gross area = 12 × 8 × 4 = 384 sq ft; subtract 21 sq ft of openings → 363 sq ft net.
- Apply waste factor: 363 × 1.1 = 399.3 sq ft.
- Divide by 32 sq ft per sheet: 399.3 ÷ 32 = 12.48, rounded up to 13.
13 sheets of 4x8 drywall (net wall area 363 sq ft).
Frequently asked questions
- What sheet size does the calculator assume?
- It assumes standard 4 ft × 8 ft sheets, which cover 32 sq ft each. If you plan to use 4x12 sheets, you will need fewer pieces, but the total square footage of drywall remains the same.
- Why add a 10% waste factor?
- Cutting around outlets, corners, and openings always leaves offcuts you cannot reuse, and some sheets get damaged. The built-in 1.1 multiplier adds 10% so you are not caught one sheet short partway through hanging.
- How do I enter doors and windows?
- Add up the area of all openings (for example a 21 sq ft door plus windows) and enter that single combined number. The calculator subtracts it from the gross wall area before applying waste.
- Does this include ceilings?
- No, it estimates walls only. To include a ceiling, treat it as an additional "wall" by entering its length and width as the dimensions and counting it in the number of surfaces.