Paint & Flooring
Drywall Calculator
Work out how much drywall you need for a room, a basement or a whole house. Enter each room’s size, wall height, doors and windows, and this drywall calculator counts the sheets (sheetrock) for walls and ceilings, plus screws, joint tape and compound, with an optional cost.
Result
Enter your measurements and press Calculate. What to buy, the working and the cost will appear here.
How to use the drywall calculator
- Enter each room: length, width and wall height, plus the number of doors and windows.
- Untick Include the ceiling if the ceiling is staying.
- Choose the sheet size. Longer sheets mean fewer seams to tape.
- Set the allowance (10–15%) and add prices for sheets, compound, tape and screws, then press Calculate.
How many sheets of drywall do I need?
wall area = 2 × (length + width) × height − doors − windows
sheets = (wall area + ceiling area) × (1 + allowance) ÷ sheet area
A 4 × 8 ft sheet covers 32 ft², a 4 × 12 ft sheet 48 ft². A 12 × 12 ft room with 8 ft walls, one door and one window has 349 ft² of wall and a 144 ft² ceiling: 493 ft² × 1.1 ÷ 32 = 17 sheets of 4 × 8.
Worked example: a 12 × 12 ft bedroom
A 12 ft × 12 ft bedroom with 8 ft walls, one door, one window and the ceiling, using 4 × 8 ft sheets at $15 and compound at $18 a bucket:
- Room 1 walls: 2 × (12 ft + 12 ft) × 8 ft − openings 35 ft² = 349 ft²
- Room 1 ceiling: 12 ft × 12 ft = 144 ft²
- Sheets: 493 ft² × 1.1 ÷ 32 ft² per sheet → 17 sheets
- Finishing: screws, tape and compound from the installed area of 493 ft²
Drywall sheets: 17 sheets; Area to cover: 493 ft²; Joint compound: 2 × 4.5 gal bucket; Joint tape: 1 roll of 250 ft; Screws: 493; Estimated cost: $291.00. Open this example in the calculator.
Drywall sheet sizes
| Sheet | Covers | Best for |
|---|---|---|
| 4 × 8 ft | 32 ft² | DIY, small rooms, easy to carry and fit in a vehicle |
| 4 × 10 ft | 40 ft² | 9 ft ceilings when hung vertically |
| 4 × 12 ft | 48 ft² | Long walls with fewer butt joints; usually needs two people |
Use 1/2 in board for most walls, 5/8 in where fire-rated board is required (often garages adjoining living space) and moisture-resistant board in bathrooms; your local code decides.
Screws, tape and joint compound
- Screws: about 1 per square foot, or 32 per 4 × 8 sheet at 16 in stud spacing. 1 1/4 in coarse-thread screws for 1/2 in board on wood studs.
- Joint tape: roughly 370 ft per 1,000 ft² of drywall, paper or mesh.
- Joint compound: around 10 gallons of premixed compound per 1,000 ft² for taping and two finish coats; a 4.5 gallon bucket finishes about 450 ft².
- Corner bead for every outside corner, measured in linear feet.
Hanging drywall
- Ceilings first, then walls, so the wall sheets support the ceiling edges.
- Hang wall sheets horizontally in most rooms: fewer linear feet of seams, and the seams fall at a comfortable height to finish.
- Stagger butt joints and avoid seams lined up with the edges of doors and windows, where cracks start.
Assumptions and limitations
- Rooms are rectangles with one wall height; add gables or soffits as extra rooms or extra area.
- Openings are subtracted using a standard door (20 ft²) and window (15 ft²); sheets are often hung over small windows and cut out, which the allowance covers.
- Supply quantities are typical rules of thumb for a standard three-coat finish.
Drywall questions
How many sheets of drywall do I need for a 12 × 12 room?
With 8 ft walls, one door and one window, walls and ceiling total about 493 ft²: 17 sheets of 4 × 8 ft or 12 sheets of 4 × 12 ft with a 10% allowance.
How many screws per sheet of drywall?
About 32 for a 4 × 8 ft sheet on walls (screws every 16 in along studs at 16 in centers), and a few more on ceilings, where spacing is closer.
How much joint compound do I need?
Roughly 1 gallon of premixed compound per 100 ft² of drywall for a full three-coat finish.
Formulas, unit conversions and default values are explained on our methodology page. Results are estimates; check manufacturer data and local codes before you buy or build.