Drywall Calculator
Enter a room, or a total wall length, and get the sheets of drywall to buy in 4×8, 4×10 or 4×12 ft, with doors and windows subtracted, plus joint compound, tape and screws.
Sheets = (wall area − openings + ceiling area) × (1 + waste) ÷ sheet area, rounded up. A 4×8 ft sheet is 32 ft², a 4×10 is 40 ft² and a 4×12 is 48 ft². Tape, compound and screws are calculated from the board area, per 1,000 ft².
Example: walls of a 14 ft × 12 ft room, 8 ft high, minus one door (20 ft²) and two windows (12 ft² each), are 416 − 44 = 372 ft². With 10% waste that is 409.2 ft², or 13 sheets of 4×8.
Method
How this calculator works
Sheet counts are plain area division. Finishing quantities use per-1,000 ft² rates published by gypsum-board makers, shown here so you can check them.
Board area to cover
Walls are the perimeter times the height. Doors and windows are subtracted at nominal sizes you can edit: 3 ft × 6 ft 8 in is 20 ft², 3 ft × 4 ft is 12 ft². The ceiling is length × width.
Walls = 2 × (L + W) × Height − OpeningsCeiling = L × WWaste and sheet count
Waste covers cuts and damage. The calculator starts at 10% and lets you pick 0 to 30%; installers commonly use 10 to 15%, but no manufacturer sets it. Sheets always round up, and the results compare 4×8, 4×10 and 4×12 so you can see the effect of longer sheets.
Sheets = round up (Area × (1 + Waste ÷ 100) ÷ Sheet area)Tape and joint compound
Per 1,000 ft² of board, the CGC/USG Construction Handbook gives 370 ft of joint tape, 138 lb of all-purpose ready-mixed compound or about 9.5 gal of lightweight compound. Georgia-Pacific lists 350 ft of tape and two 61 lb pails of all-purpose compound, within about 6% of the handbook.
Tape (ft) = Area × 0.37Lightweight compound (gal) = Area × 0.0095All-purpose compound (lb) = Area × 0.138Screws
The same handbook lists about 1,000 screws per 1,000 ft² of single-layer board on framing at 16 in on center, and about 850 at 24 in. The calculator uses these totals, not a fastener-spacing diagram, and suggests buying about 10% extra.
Screws (16 in o.c.) = Area × 1.0Screws (24 in o.c.) = Area × 0.85Worked example: walls of a 14 ft × 12 ft room, 8 ft high
Arithmetic checkedOne door (20 ft²), two windows (12 ft² each), 10% waste, framing at 16 in on center.
| Step | Math | Result |
|---|---|---|
| Wall area | 2 × (14 + 12) × 8 | 416 ft² |
| Openings | 1 × 20 + 2 × 12 | 44 ft² |
| Board area to cover | 416 − 44 | 372 ft² |
| Add 10% waste | 372 × 1.10 | 409.2 ft² |
| Sheets of 4×8 (32 ft²) | 409.2 ÷ 32 = 12.79, round up | 13 sheets |
| Sheets of 4×10 (40 ft²) | 409.2 ÷ 40 = 10.23, round up | 11 sheets |
| Sheets of 4×12 (48 ft²) | 409.2 ÷ 48 = 8.53, round up | 9 sheets |
| Joint tape | 372 × 0.37 | 137.6 ft |
| Lightweight compound | 372 × 0.0095 | 3.53 gal |
| Screws | 372 × 1.0 | 372 screws |
| You would buy | 13 sheets of 4×8, about 138 ft of tape, 3.6 gal of compound | |
Add the 14 ft × 12 ft ceiling (168 ft²) and the board area is 540 ft². With 10% waste that is 594 ft², or 19 sheets of 4×8.
Disclaimer
Results are planning estimates based on the dimensions and assumptions you enter. They are not engineering, structural or building-code advice. Product yields, densities and coverage vary by manufacturer, batch and site conditions. Check product labels, your supplier and your local building department before you order materials or start work. Read the full calculation disclaimer.
Accuracy
What affects your estimate
Sheet count follows from area. The finishing materials depend on how you work and how smooth the wall has to be.
Openings
Many installers skip openings under about 32 ft² because the cut-outs make useful offcuts. Set the door and window counts to 0 to do the same. Large openings are worth subtracting.
Finish level and texture
The compound rate is for a standard finish. Georgia-Pacific puts texturing at an extra 15 to 50 lb per 1,000 ft². Skim coats and a higher finish level use more compound than the calculator shows.
Sheet length and joints
Longer sheets mean fewer seams to tape. They are also heavier and harder to carry and hang. Compare the counts for all three sizes, then choose what you can handle.
Layout and cuts
Installers commonly use 10 to 15%. Odd room shapes, many corners and small walls leave more offcuts that cannot be reused, so they belong at the top of that range.
Moisture-resistant board in wet areas, fire-rated (Type X) assemblies and their fastener patterns follow the assembly listing and your local code. Sanding drywall makes dust: wear a respirator.
Common mistakes
Forgetting the ceiling
The tool has separate options for walls only, ceiling only and walls plus ceiling. Pick the one that matches the job, or the sheet count will be short.
Skipping the waste allowance
Cuts at corners, outlets and window returns waste board. At 0% every cut has to land perfectly, and a second trip for one missing sheet is a nuisance.
Treating the mud rate as exact
The compound figure is a manufacturer average for a standard finish. Heavy texture, skim coating and repairs push it up.
Questions people ask
How many sheets of drywall do I need?
Divide the board area, with waste, by the sheet area: 32 ft² for 4×8, 40 ft² for 4×10, 48 ft² for 4×12. Round up. For 372 ft² and 10% waste, that is 13 sheets of 4×8. The guide on how many sheets of drywall you need adds a room table and tape, mud and screw amounts.
How do I calculate drywall for a room?
Walls: 2 × (length + width) × height. Subtract doors and windows, add the ceiling (length × width), add waste, then divide by the sheet size. Once the board is up, the paint calculator turns the same room into gallons, and the guide on how many square feet a gallon of paint covers explains the coverage.
How much joint compound do I need?
About 9.5 gal of lightweight compound or 138 lb of all-purpose compound per 1,000 ft² of board. For 540 ft² that is about 5.1 gal or 74.5 lb.
Should I subtract windows and doors?
Large openings, yes. Many installers ignore ones under about 32 ft² because the cut-outs are reusable. The calculator subtracts what you enter, and zero counts turns it off.
Is a 4×12 sheet better than a 4×8?
It means fewer joints to tape on long walls, and the results show the count for all three sizes. Weight and handling matter too, so choose what you can hang.
Related calculators and guides
Sources
Where the numbers come from
- CGC/USG Construction Handbook chapter 3, joint treatment for gypsum panels (tape, compound, screws), accessed October 16, 2026.
- Georgia-Pacific (manufacturer guide, used as a cross-check) ToughRock gypsum board Wallworks guide (tape, compound, texture), accessed October 16, 2026.
- USG FAQ on lightweight joint compound per 1,000 sq. ft., accessed October 16, 2026.