Drywall sheets come in 4 × 8, 4 × 10 and 4 × 12 ft sizes (1200 × 2400 mm elsewhere). Longer sheets mean fewer seams to tape, but they are heavy to handle. Subtract large openings, then add about 10–15% for cut-offs. Screws, tape and joint compound scale with the drywall area.
How to use the Drywall Calculator
- Room length
- Room width
- Wall height
- Include ceiling
- Doors (3 × 7 ft)
- Windows (3 × 5 ft)
- Sheet size
- Waste
- Price per sheet
- Price per pail of compound
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the room length, width and wall height, whether to include the ceiling, the number of doors and windows, the sheet size and waste. The calculator works out the net area, number of sheets, screws, rolls of tape and pails of compound, and the cost at your sheet price.
Tips for an accurate estimate
- Sketch the job and split irregular areas into rectangles, circles and triangles before you measure.
- Add a waste allowance – typically 5–10% for simple layouts and 15–20% for diagonal, curved or heavily cut work.
- Check the coverage or yield printed on the product, because sizes and densities vary between manufacturers.
- Buy all units of a finished material (tile, brick, siding) from the same batch so colours match, and keep a few spares for repairs.
- Confirm local prices – quarry, lumber and steel prices vary widely by region and season.
Common mistakes to avoid
- Ordering exactly the calculated amount with no allowance for breakage, offcuts and settlement.
- Forgetting to subtract doors, windows and other openings – or subtracting small ones that still need cutting around.
- Confusing US short tons (2,000 lb) with metric tonnes (1,000 kg) when comparing quotes.
Inputs explained
| Field | What to enter |
|---|---|
| Room length | Units: ft, m, in, yd, cm |
| Room width | Units: ft, m, in, yd, cm |
| Wall height | Units: ft, m, in, yd, cm |
| Include ceiling | Choose one: No, Yes |
| Doors (3 × 7 ft) | A number |
| Windows (3 × 5 ft) | A number |
| Sheet size | Choose one: 4 × 8 ft, 4 × 10 ft, 4 × 12 ft, 54 in × 12 ft … |
| Waste | In % |
| Price per sheet | Units: /piece |
| Price per pail of compound | Units: /piece |
What each result means
- Wall area (net) = max(2×([Room length] + [Room width])×[Wall height] – [Doors (3 × 7 ft)]×1.9509638400000002 – [Windows (3 × 5 ft)]×1.3935456000000002, 0)
- Ceiling area = [Include ceiling]×[Room length]×[Room width]
- Drywall sheets = ceil(([Wall area (net)] + [Ceiling area])×(1 + [Waste]÷100)÷[Sheet size])
- Drywall screws = ceil(([Wall area (net)] + [Ceiling area])÷0.09290304)
- Joint tape (250 ft rolls) = ceil(([Wall area (net)] + [Ceiling area])÷0.09290304×0.37÷250)
- Joint compound (4.5 gal pails) = ceil(([Wall area (net)] + [Ceiling area])÷0.09290304÷450)
- Material cost = [Drywall sheets]×[Price per sheet] + [Joint compound (4.5 gal pails)]×[Price per pail of compound]
Example values
How the main result changes when Room length changes and everything else stays at the example values above:
| Room length (ft) | Drywall sheets |
|---|---|
| 7 | 12 |
| 10.5 | 15 |
| 14 | 19 |
| 17.5 | 22 |
| 21 | 26 |
| 28 | 32 |
Formula
Wall area = 2 (L + W) × H − doors × 21 ft² − windows × 15 ft²Sheets = (walls + ceiling) × (1 + waste) ÷ sheet areaScrews ≈ 1 per ft²; tape ≈ 0.37 ft per ft²; compound ≈ one 4.5-gal pail per 450 ft²Worked example
Inputs — Room length: 14 ft; Room width: 12 ft; Wall height: 8 ft; Include ceiling: Yes; Doors (3 × 7 ft): 1; Windows (3 × 5 ft): 2; Sheet size: 4 × 8 ft; Waste: 10 %; Price per sheet: $15 /piece; Price per pail of compound: $20 /piece.
Results — Wall area (net) = 365 ft²; Ceiling area = 168 ft²; Drywall sheets = 19; Drywall screws = 533; Joint tape (250 ft rolls) = 1; Joint compound (4.5 gal pails) = 2; Material cost = $325.00.
Key terms
- Drywall
- Gypsum board, also called plasterboard, wallboard or sheetrock.
Frequently asked questions
How many sheets of drywall for a 12 × 12 room?
Walls 8 ft high plus ceiling = 528 ft²; less a door and window ≈ 492 ft² ≈ 17 sheets of 4 × 8 with 10% waste.
How many screws per sheet of drywall?
About 32 for a 4 × 8 sheet on walls (studs 16 in o.c.) – roughly one per square foot.
Should I hang drywall horizontally or vertically?
Horizontally on walls is common: it reduces seam length and bridges uneven studs. Commercial jobs often hang vertically for fire-rated assemblies.
What thickness of drywall should I use?
½ in for walls, ⅝ in (Type X) for ceilings with 24 in framing, garages and fire-rated walls.
What formula does the Drywall Calculator use?
Wall area = 2 (L + W) × H − doors × 21 ft² − windows × 15 ft².