This drywall calculator computes how many sheets a room needs — walls plus ceiling — from the room’s dimensions and your sheet size, so you can order once instead of twice.
How Drywall Estimating Works
Drywall covers surfaces, so the estimate is an area problem: wall area is the room’s perimeter times ceiling height, the ceiling is length × width, and the sheet count is the total divided by the sheet’s area — always rounded up. Ordering a couple of extra sheets is standard: cuts, mistakes and damaged corners eat sheets, and returning one unopened sheet beats a mid-job store run. This calculator is part of our Construction Calculators collection; the room’s finish coat quantities live in the Paint Calculator.
Worked Example (Verified)
A 12 × 15 ft room, 8 ft ceilings, ceiling included:
- Walls: 2 × (12 + 15) × 8 = 432 sq ft; ceiling: 180 sq ft; total 612 sq ft
- 4×8 sheets (32 sq ft): 612 ÷ 32 = 19.1 → 20 sheets
- Screws at ~32 per sheet: ≈640 — buy a 5 lb box and be done
Sheet Choices and Practical Notes
- 4×8 is the DIY standard (one person can almost handle it); 4×12 means fewer seams on long walls but is a two-person, stair-unfriendly board.
- Thickness: ½″ for most walls, ⅝″ fire-rated where code asks (garage walls, multi-family), ¼″ for curved overlays.
- Openings: many pros do not subtract doors and windows — the cut-out waste rarely converts into usable pieces, and the difference is usually a sheet. Use the openings field for big picture windows and open-plan sides.
- Ceilings first, walls hung top-down, seams staggered — and compound needs roughly 0.05 lb per sq ft per coat if you are estimating mud too (a 5-gallon bucket covers ~350–400 sq ft of finished work, tape embedded).
Related Tools
- Paint Calculator — the finish after the board
- Construction Calculators — the full collection
Frequently Asked Questions
How many drywall sheets do I need for a 12×12 room?
Walls: 2 × 24 × 8 = 384 sq ft; ceiling: 144; total 528 sq ft → 528 ÷ 32 = 16.5 → 17 sheets of 4×8 (plus a spare).
Should I subtract doors and windows?
For rough orders, no — waste absorbs them. Subtract only large openings (sliding doors, open walls) or when the bid must be exact.
How many screws per drywall sheet?
About 28–32 for a 4×8 on walls (16″ stud spacing, screws every 12″ in the field, 8″ on edges). Ceilings take more — every 7–8″ is common guidance.
4×8 or 4×12 sheets?
4×12s reduce seams and taping on long, straight walls but weigh ~25% more per sheet and fight you in stairwells. Most garages and single rooms are happier with 4×8 or 4×10.
How much joint compound do I need?
Roughly one 5-gallon bucket per 350–400 sq ft of finished drywall across all coats, plus a roll of tape per ~370 linear feet of seam.
Is this drywall calculator free?
Yes — free, instant, no sign-up.