How to calculate drywall
For a room, wall area equals perimeter × height. Add length × width when covering the ceiling. For one wall, multiply wall length by height.
Drywall formula
Sheets = total surface area ÷ sheet area. The calculator rounds up both the base estimate and the estimate after applying your waste percentage.
Worked example
A 12 × 10 foot room with 8-foot walls has 352 square feet of wall area. Adding its 120-square-foot ceiling gives 472 square feet. Using 4 × 8 sheets requires 15 before waste and 17 with 10% waste.
Practical tips
- Longer sheets may reduce seams but are heavier and harder to maneuver.
- Do not automatically subtract doors and windows; offcuts are often needed elsewhere.
- Plan sheet orientation, framing locations, and moisture- or fire-resistant board requirements before ordering.
Assumptions and limitations
The estimate is area-based and does not model framing layout, openings, staggered seams, or unusable offcuts. Sheet counts round up.
Frequently asked questions
What drywall sheet sizes are common?
Four-foot-wide sheets in 8-, 10-, and 12-foot lengths are common. Availability and thickness vary.
How much waste should I include?
About 10% is a common planning allowance, with more potentially needed for complex layouts or many small cuts.