Drywall Calculator
This free drywall calculator (sheetrock calculator) turns a room's length, width and wall height into the number of drywall sheets you need, plus joint compound, tape, screws and a cost range. Doors and windows are subtracted, and the ceiling is optional.
What this calculator does
This planner works out how much drywall a room needs, and everything that goes with it: sheets, joint compound, paper tape and screws. You get a shopping list you can take to the store, and a cost range for doing it yourself versus hiring a contractor to hang and finish it.
How the math works
- Wall area: 2 × (length + width) × wall height, minus 21 sq ft per door (3 × 7 ft) and 15 sq ft per window (3 × 5 ft).
- Board area: wall area plus the ceiling (length × width), if included.
- Sheets: board area plus your waste allowance (10% by default), divided by one sheet's area, rounded up.
- Joint compound: one 4.5 gal pail per ~450 sq ft of board. Tape: ~370 ft per 1,000 sq ft, in 500 ft rolls. Screws: ~1 per sq ft, ~320 per pound.
Worked example
A 12 × 12 ft bedroom with 8 ft walls, one door and two windows, ceiling included. Walls: 2 × 24 × 8 = 384 sq ft, less 21 + 30 for openings = 333 sq ft. Add the 144 sq ft ceiling for 477 sq ft of board. With 10% waste that's 524.7 sq ft ÷ 32 = 16.4, so 17 sheets of 4 × 8 drywall, plus 2 pails of joint compound, 1 roll of tape and 2 lb of screws. Expect about $253–$383 in materials, or $954–$1,670 hung and finished by a pro.
Frequently asked questions
How many sheets of drywall do I need?
Add the wall area (perimeter × height, less openings) and the ceiling, add 10% for waste, then divide by the sheet size: 32 sq ft for 4 × 8, 48 sq ft for 4 × 12. A 12 × 12 ft room with a ceiling, one door and two windows needs about 17 sheets of 4 × 8.
How much drywall mud do I need?
Roughly one 4.5 gal pail of all-purpose joint compound per 450 sq ft of drywall for a three-coat finish. A 12 × 12 ft room with a ceiling needs about 2 pails.
How many screws per sheet of drywall?
About one per square foot, so around 32 for a 4 × 8 sheet on walls with studs 16 in apart. Ceilings take a few more because screws go every 12 in. A pound of 1-1/4 in screws is about 320 screws.
Should I use 4 × 8 or 4 × 12 drywall sheets?
Longer sheets mean fewer seams to finish, but a 4 × 12 sheet weighs around 70 lb and is awkward through doors and up stairs. For a DIY job, especially overhead, 4 × 8 is usually easier.
How much does it cost to drywall a room?
DIY materials run about $0.50–$0.80 per sq ft of board. A contractor typically charges about $2.00–$3.50 per sq ft to hang, tape and finish, materials included. For a 12 × 12 ft room with a ceiling, that's roughly $250–$380 DIY or $950–$1,700 installed.
Limitations
This tool assumes a rectangular room with flat walls and ceiling, standard-size doors and windows, and 1/2 in regular drywall. It doesn't plan sheet layout, and it doesn't include corner bead, moisture-resistant or fire-rated board (often required in bathrooms, garages and between units), primer, or tools. Finishing quantities are rules of thumb; actual use depends on finish level and skill. Check local code for where 5/8 in fire-rated board is required.
Put this calculator on your site
Run a blog or business site for DIYers, homeowners or contractors? You can embed the Drywall Calculator as a free widget — responsive, no registration, and no ads or tracking added to your page.
Cite this calculator
Using this tool in a class, a paper or an article? Copy a ready-made reference: