Drywall Calculator
Calculate exactly how many drywall sheets you need for walls and ceilings. This free calculator accounts for doors, windows, and includes a 10% waste factor plus joint tape estimates for complete project planning.
How to Use This Drywall Calculator
- Measure and enter your room dimensions: length, width, and wall height in feet
- Select your preferred drywall sheet size (4x8 for standard rooms, 4x12 for fewer seams)
- Check the ceiling option if you're also covering the ceiling with drywall
- Enter the number of doors and windows to subtract their area from the total coverage
- Review the total sheets needed, which includes a 10% waste factor for cuts and mistakes
For multiple rooms, calculate each room separately and add the totals together. This gives you a more accurate estimate since each room's openings differ.
What is a Drywall Calculator?
A drywall calculator is a project planning tool that estimates the number of drywall sheets (also known as sheetrock, gypsum board, or wallboard) required for construction or renovation projects. Drywall is the standard material for interior walls and ceilings in residential and commercial buildings, consisting of gypsum plaster pressed between two sheets of thick paper.
The calculator determines your wall and ceiling coverage needs, subtracts openings for doors and windows, and adds an industry-standard waste factor to ensure you purchase enough material. Running short during a project means delays while waiting for additional materials, so the 10% waste factor accounts for cuts around outlets, corners, damaged pieces, and cutting mistakes.
Choosing the Right Drywall Type
Different areas of your home may require different types of drywall:
- Standard (White Board): 1/2" thick for most walls and ceilings. The most common and economical choice
- Moisture-Resistant (Green Board): Contains water-resistant additives. Use in bathrooms, laundry rooms, and kitchens but not in direct water contact areas
- Fire-Resistant (Type X): 5/8" thick with fire-resistant additives. Required by code for garage walls, furnace rooms, and between floors in multi-story homes
- Soundproof: Denser composition that reduces sound transmission. Ideal for bedrooms, home offices, and media rooms
- Lightweight: Easier to handle and install. Great for ceilings and DIY projects
Drywall Calculation Formula
The formula for calculating drywall sheets:
Sheets = (Total Sq Ft x 1.10) / Sheet Size
Where Total Square Feet includes:
- Wall Area: Perimeter x Height - (Doors x 21 sq ft) - (Windows x 15 sq ft)
- Ceiling Area: Length x Width (if included)
- Joint Tape: Approximately 12 feet of tape per drywall sheet
Standard sheet sizes: 4x8 feet (32 sq ft) or 4x12 feet (48 sq ft). Larger 4x12 sheets mean fewer seams to tape but are heavier and harder to maneuver.
Drywall Thickness Guide
- 1/4" drywall: For curved walls and as a layer over damaged existing walls
- 3/8" drywall: For repair work and double-layer applications
- 1/2" drywall: Standard thickness for walls with 16" stud spacing
- 5/8" drywall: For ceilings to prevent sagging, fire-rated applications, and walls with 24" stud spacing
Additional Materials Needed
Beyond drywall sheets, your project will require:
- Joint compound (mud): Approximately 1 gallon per 100 square feet for three coats
- Joint tape: About 12 feet per sheet of drywall installed
- Drywall screws: Use 1-1/4" screws for 1/2" drywall, placed every 8" along studs
- Corner bead: Metal or paper for outside corners
- Sanding supplies: Screens or sandpaper for finishing
Pro Installation Tips
- Hang ceiling drywall first, then walls. Wall sheets help support ceiling edges
- Stagger seams between rows to add strength and reduce visible joints
- Keep horizontal seams at 48" height to match standard sheet width
- Leave 1/2" gap at floor level for expansion and to prevent moisture wicking
- Score and snap cuts rather than sawing for faster, cleaner edges