Drywall Calculator
Estimate how many drywall sheets, screws, joint tape, and compound you need for a room — based on total wall and ceiling area.
What is a drywall calculator?
The drywall calculator estimates how many sheets of gypsum board to buy, plus the screws, joint tape, and mud you'll need to finish a room. It works from the wall perimeter, ceiling height, and ceiling area, minus the openings for doors and windows.
Formula
Wall area = wall length × ceiling height
Net area = wall area + ceiling area − door & window openings
Sheets = ceil(net area × (1 + waste) / sheet size)
Rules of thumb for finishing supplies:
- Screws: ~32 per sheet (16 in framing)
- Paper tape: ~0.55 linear ft per sq ft of board
- Joint compound: ~1 gallon per 100 sq ft for three coats — one 5-gal bucket covers ~500 sq ft
Worked example
A 12×15 ft bedroom with 8 ft ceilings, two openings totaling 40 sq ft, using 4×8 sheets with 10% waste:
- Wall length = 2 × (12 + 15) = 54 ft → wall area = 54 × 8 = 432 sq ft
- Ceiling area = 12 × 15 = 180 sq ft
- Net area = 432 + 180 − 40 = 572 sq ft
- Sheets = ceil(572 × 1.10 ÷ 32) = 20 sheets
- Screws ≈ 640, tape ≈ 315 ft, compound ≈ 1.9 five-gallon buckets
How to use this calculator
- Measure the perimeter of the room (sum of wall lengths) and ceiling height.
- Calculate ceiling area (length × width).
- Subtract door and window openings — standard door ≈ 21 sq ft, standard window ≈ 15 sq ft.
- Pick your sheet size (4×12 for pro jobs; 4×8 for DIY — easier to carry).
- Keep the waste allowance at 10% for square rooms, 15% for complex layouts.
Frequently asked questions
Which sheet size should I buy?
4×8 is easiest for DIY — one person can maneuver it. 4×12 creates fewer seams to tape and is faster for pros, but requires two people and a longer straight hallway to carry in.
What thickness of drywall for walls vs ceilings?
Walls: 1/2" standard. Ceilings: 5/8" is preferred — it sags less over time and is required in some fire-rated assemblies. Use moisture-resistant ("green board") in bathrooms and mold-resistant ("purple") where moisture is a concern.
How much joint compound for three coats?
Plan on 1 gallon per 100 sq ft total for three coats (tape, fill, finish). A 5-gallon bucket covers ~500 sq ft. Pre-mixed "All-Purpose" is easiest for DIY; "Lightweight" (Easy Sand) is lower-effort to sand.
Do I need Type X fire-rated board?
Required for walls shared with attached garages, furnace rooms, and some stairwell assemblies under the International Residential Code. Check your local building code before buying.