How to calculate drywall
Wall area = 2 × (Length + Width) × Height
Total = Wall area + Ceiling (Length × Width) − Doors (≈ 21 sq ft each) − Windows (≈ 15 sq ft each)
Sheets = Total × (1 + Waste) ÷ Sheet area (32, 40 or 48 sq ft), rounded up
Example: a 12 × 10 ft room with 8 ft walls has 352 sq ft of wall and 120 sq ft of ceiling. Taking off one door and one window leaves 436 sq ft. With 10% waste, that's 15 sheets of 4 × 8 drywall.
Drywall tips
- Longer sheets mean fewer seams to tape, but 4 × 12 sheets weigh about 80 lb and need two people.
- Thickness: 1/2" for walls, 5/8" for ceilings with joists 24" apart and fire-rated walls (such as between a garage and the house).
- Moisture-resistant board for bathrooms; cement board behind tile in showers.
- Screws go about every 12" on ceilings and 16" on walls, roughly one per square foot overall.
Painting after? Use the paint calculator.
Frequently asked questions
How many sheets of drywall for a 12×12 room?
With 8 ft walls and the ceiling, about 528 sq ft before openings, or roughly 17 sheets of 4 × 8 with 10% waste and one door and window removed.
Should I subtract doors and windows?
Yes for a closer count, but many pros only subtract large openings because the cutouts become waste anyway. The waste allowance covers it either way.
How much does drywall cost?
Standard 1/2" 4 × 8 sheets typically cost $15 to $20 each, before tape, mud, screws and labor. Enter your local price to see the total.
Was this calculator helpful?