Drywall Calculator
This drywall calculator works out how many sheets of drywall you need for a room's walls and ceiling. Pick 4×8, 4×10 or 4×12 sheets, and it adds a waste allowance for cuts and rounds up to whole sheets.
Result
19 sheets of 4×8 drywall
| Wall area | 384 ft² |
|---|---|
| Ceiling area | 144 ft² |
| Total area | 528 ft² |
| Area per sheet | 32 ft² |
| Waste allowance | 10% |
Results update as you type.
How Much Drywall Do I Need?
To estimate drywall, add up the surface area of every wall (and the ceiling, if you’re doing it) and divide by the area of one sheet. Add a waste allowance for cuts, then round up. The calculator handles a rectangular room in one go. Here’s how to do it by hand.
How to Calculate Drywall by Hand
1. Wall area
Wall area (ft²) = 2 × (length + width) × wall height
2. Ceiling area (optional)
Ceiling area (ft²) = length × width
3. Sheets
Sheets = (wall area + ceiling area − openings) × (1 + waste) ÷ sheet area, rounded up
Sheet areas are 32 ft² for a 4×8, 40 ft² for a 4×10 and 48 ft² for a 4×12.
Worked example: a 12 × 14 bedroom with 4×12 sheets
Eight foot walls, walls and ceiling, 10% waste:
- Walls: 2 × (12 + 14) × 8 = 416 ft²
- Ceiling: 12 × 14 = 168 ft²
- Total: 584 ft²
- With waste: 584 × 1.10 = 642.4 ft²
- Sheets: 642.4 ÷ 48 = 13.4, rounded up to 14 sheets of 4×12
The same room in 4×8 sheets is 642.4 ÷ 32 = 20.1, which rounds up to 21 sheets. Fewer, longer sheets means fewer seams to finish.
Tips & Common Mistakes
Hang the ceiling first
The wall sheets then hold up the edges of the ceiling sheets, and the corner joint is tighter. A drywall lift, which you can rent, makes a ceiling far easier for one or two people.
Hang walls horizontally
On 8 foot walls, two 4 foot sheets run horizontally cover the height exactly. The joint lands at a comfortable working height, and you get fewer vertical butt joints to finish. On 9 foot walls, use 54 inch-wide board where you can find it, or plan a rip strip.
Stagger the butt joints
Don’t line up the ends of sheets on the same stud in neighboring rows. Staggered butt joints are much less likely to crack and are easier to feather out.
Account for closets and soffits separately
Closets, soffits and bulkheads add a lot of surface area for their size. Measure each one as its own small “room” and add the sheets together, rather than guessing.
The calculator stops at the sheets
Tape, joint compound, corner bead and screws depend on how many joints and corners you have and on your framing. Check the coverage on each product’s packaging. When the walls are finished, our paint calculator tells you how much primer and paint to buy. New drywall always needs primer.
Frequently Asked Questions
How many sheets of drywall do I need for a 12x12 room?
With 8 foot walls, the walls are 384 square feet and the ceiling is 144 square feet. With 10% waste, that is 19 sheets of 4 by 8 drywall for walls and ceiling, or 14 sheets for the walls alone.
How many sheets of drywall do I need for a 10x10 room?
With 8 foot walls, the walls are 320 square feet. With 10% waste that is 11 sheets of 4 by 8 drywall. Adding the 100 square foot ceiling brings it to 15 sheets.
Should I subtract doors and windows when estimating drywall?
Many drywallers don't subtract ordinary doors and windows. The cutouts are rarely usable, and sheets usually run across the openings. Subtract large openings such as patio doors or wide archways, where you will really save material.
Is it better to use 4x8 or 4x12 drywall sheets?
Longer sheets mean fewer joints to tape and finish, which saves time and gives a smoother wall. But 4 by 12 sheets are heavy and hard to get up stairs and around corners. Many DIYers use 4 by 8 sheets for walls and longer sheets for ceilings, where they have help.
How much extra drywall should I buy?
Add about 10% for an average room. Go to 15% for rooms with many corners, soffits or angled ceilings. A spare sheet is handy for fixing a bad cut and costs much less than a second trip to the store.
What thickness of drywall should I use?
Half-inch drywall is standard for interior walls. Ceilings often use half-inch sag-resistant board or 5/8 inch board, depending on joist spacing. Fire-rated Type X board is required in some places, such as walls between a garage and the house. Check your local code.
Related Calculators
Sources & Assumptions
- Standard drywall panels are 4 ft wide in 8, 10 and 12 ft lengths (32, 40 and 48 ft²).
- Sheets = (wall area + ceiling area − openings) × (1 + waste) ÷ sheet area, rounded up. Default waste is 10%.
- Screws, tape and joint compound are not estimated. Fastener spacing depends on framing and code; follow the panel manufacturer's instructions and Gypsum Association GA-216.
- Areas are rounded only for display. Sheet counts always round up.
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