Drywall Calculator — How Many Sheets of Drywall Do I Need?
Calculate the exact number of drywall sheets, joint compound, tape, screws, and corner bead needed for any room. Supports walls and ceilings with door and window deductions.
How to Use This Calculator
- Enter your room dimensions (length, width, ceiling height)
- Choose whether to include the ceiling in the estimate
- Select your sheet size and drywall thickness
- Enter the number of doors and windows to deduct their areas
- Click "Calculate Drywall" for a complete material list
How the Calculation Works
wall_area = 2 × (length + width) × ceiling_height
door_area = num_doors × 21 // standard 3×7ft door ≈ 21 sqft
window_area = num_windows × 15 // average window ≈ 15 sqft
ceiling_area = (include_ceiling) ? length × width : 0
total_area = wall_area - door_area - window_area + ceiling_area
sheet_area = 4 × sheet_length // 4×8 = 32 sqft | 4×12 = 48 sqft
sheets_needed = ceil((total_area / sheet_area) × (1 + waste))
joint_compound_gallons = total_area / 100
tape_rolls = ceil(total_area / 500) Wall area is calculated by multiplying the perimeter (2 × length + width) by the ceiling height. Door and window areas are subtracted. If including the ceiling, its area is added. Total area is divided by sheet area and rounded up. Joint compound coverage is approximately 100 sqft per gallon and tape covers 500 sqft per roll.
Variables:
- total_area: Net area of all walls and ceiling after deducting openings
- sheet_area: Area of one drywall sheet (4×8 = 32 sqft, 4×12 = 48 sqft)
- sheets_needed: Total sheets to purchase, rounded up with waste factor
- joint_compound_gallons: Pre-mixed joint compound at ~100 sqft per gallon
- tape_rolls: Paper joint tape rolls at ~500 sqft coverage per roll
Pro Tips
- Hang sheets horizontally on walls — it creates fewer joints and a stronger installation
- For ceilings, use 5/8" drywall to resist sagging — 1/2" is acceptable for 16" OC framing
- Use moisture-resistant (green board) or mold-resistant (purple board) in bathrooms and laundry rooms
- Apply joint compound in 3 coats: tape coat, fill coat, finish coat — sand lightly between each
- Buy 10–15% extra drywall for waste from cuts around outlets, windows, and irregular walls
Recommended Products
Frequently Asked Questions
How many sheets of drywall for a 12×12 room?
A 12×12 room with 8ft ceilings has about 384 sqft of wall area. Subtract one door (21 sqft) and two windows (30 sqft) = 333 sqft walls. Including ceiling (144 sqft) = 477 sqft total. At 32 sqft per sheet: 15 sheets + 10% waste = 17 sheets.
What thickness drywall should I use?
1/2" for walls (most common), 5/8" for ceilings (reduced sagging), 1/4" for curved walls or over existing surfaces. In garages and attached walls, use 5/8" Type X fire-rated drywall.
How many screws per sheet of drywall?
Plan for approximately 32 screws per 4×8 sheet on walls. Screws go every 12" on the field and every 8" on edges/ceilings. A 1-pound box (~200 screws) covers about 6 sheets.
How much joint compound do I need?
Pre-mixed joint compound comes in 1-gallon and 5-gallon buckets. Plan for about 1 gallon per 100 sqft of finished drywall across all three coats. For a 500 sqft room, one 5-gallon bucket is typically sufficient.
Do I need special drywall for bathrooms?
Yes. Use moisture-resistant (green board) or mold-resistant (purple board) drywall in areas with high humidity. Never use standard drywall behind tile — use cement board (HardieBacker) for wet areas like showers and tub surrounds.