Drywall Calculator
Estimate drywall sheets, joint compound, tape, and screws for your project. Supports rectangle and L-shaped rooms with door and window deductions. Choose from 4×8, 4×9, or 4×12 sheet sizes.
How to Use This Calculator
- Choose the room shape (rectangle or L-shape) and enter the corresponding dimensions.
- Enter the ceiling height and select the drywall sheet size (4×8, 4×9, or 4×12).
- Enter the number of doors and windows — standard deductions: door = 21 sq ft, window = 15 sq ft.
- Adjust the waste factor (default 10%) to account for cuts and mistakes.
- Click "Calculate Drywall" to see total sheets, joint compound, tape, and screws needed.
Formula
Ceiling Area: Length × Width
Net Area: (Wall + Ceiling) − (Doors × 21 sq ft) − (Windows × 15 sq ft)
Sheets: ⌊(Net Area × (1 + Waste%) / Sheet Area)⌋
Joint Compound: ~1 lb per sheet (for 2 coats)
Tape: 1 roll per 3 sheets (approx. 50 ft per roll)
Screws: ~1 lb per 4 sheets (or ~2 lbs per box)
Standard door deduction is 21 sq ft (3’ × 7’). Standard window deduction is 15 sq ft (3’ × 5’). For L-shaped rooms, the calculator sums both sections for wall and ceiling area.
Examples
12 ft × 10 ft, 8 ft ceiling, 1 door, 1 window, 4×8 sheets, 10% waste: Wall = 352 sq ft, Ceiling = 120 sq ft, Net = 446 sq ft, Sheets = 16 sheets.
20 ft × 15 ft, 9 ft ceiling, 2 doors, 3 windows, 4×12 sheets, 12% waste: Wall = 630 sq ft, Ceiling = 300 sq ft, Net = 843 sq ft, Sheets = 23 sheets.
Section A: 14×10 + Section B: 8×6, 8 ft ceiling, 4×9 sheets: Wall = 528 sq ft, Ceiling = 188 sq ft, Sheets = 22 sheets with 10% waste.
Frequently Asked Questions
How many sheets of drywall do I need?
Calculate your total wall and ceiling area, subtract openings (doors and windows), add a waste factor (10–15%), then divide by the sheet area (32 sq ft for 4×8, 36 for 4×9, 48 for 4×12). Always round up to the nearest whole sheet.
How much joint compound per sheet?
Plan for approximately 1 pound of joint compound per sheet for two coats. This includes taping and finishing. Pre-mixed compound (ready-mud) typically comes in 30 lb or 50 lb buckets. One 50 lb bucket covers about 50 sheets.
What size drywall should I use?
4×8 ft is standard and easiest to handle for DIY. 4×9 ft covers more area with fewer seams. 4×12 ft is best for large rooms or commercial spaces where fewer joints mean a smoother finish. Thicker sheets (5/8”) are better for ceilings and fire-rated walls.
How to calculate drywall for an L-shaped room?
Split the L-shape into two rectangles. Calculate wall and ceiling area for each section, then add them together. This calculator does this automatically when you select “L-Shape” — just enter dimensions for both sections.