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 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.