Formula
How the drywall estimate works
- Wall area = 2 × (room length + room width) × wall height − openings
- Total board area = wall area + optional ceiling area
- Required sheets = total board area × (1 + waste %) ÷ sheet area, rounded up
Free project planning tool
Drywall calculator
Calculate drywall surface area, complete sheet quantity, waste allowance, and estimated sheet cost for a room.
✓ Metric & imperial✓ Transparent assumptions✓ No signup
Walls & ceilingsInstant estimate
Example calculation
A 12 × 10 × 8 ft room has 352 sq ft of wall area before openings. Subtract 51 sq ft of doors and windows, add a 120 sq ft ceiling, and allow 10% waste. Using 4 × 8 ft sheets, the purchase quantity rounds up to 15 sheets.
Planning tips
- Enter zero for ceiling area when only the walls will be covered.
- Choose a sheet size that fits the framing and can be safely handled.
- Complex ceilings, short offcuts, and many openings can require more waste.
Common questions
Drywall calculator FAQ
How many drywall sheets do I need?
Divide the adjusted wall and ceiling area by one sheet’s area, then round up. This calculator performs that step using your selected sheet dimensions.
Should I subtract doors and windows?
Yes for a tighter estimate. On small projects, leaving part of the opening area in the estimate can provide useful offcuts and repair stock.
What waste allowance should I use?
Ten percent is a practical starting point for a simple room. Irregular layouts, many corners, and difficult handling may need more.