Drywall Calculator

Step 1: Choose Imperial or Metric. The calculator switches all units, including the sheet-size presets — 4×8 ft and 1.2×2.4 m are the two regional standards.

Step 2: Enter each room's length, width, and ceiling height. Use "+ Add Room" to combine multiple rooms in a single estimate. Rename rooms (Bedroom, Hallway) for the breakdown table.

Step 3: Enter doors and windows per room. Defaults assume a standard 80 × 36 inch interior door (20 sqft / 1.86 sqm) and a 36 × 48 inch window (12 sqft / 1.11 sqm). The calculator subtracts these from the area to be covered.

Step 4: Toggle "Include ceiling" per room. Most full drywall jobs cover walls AND ceilings — the ceiling is included by default. Uncheck if you are only redrywalling walls and keeping the existing ceiling.

Step 5: Choose your sheet size. The US standard is 4×8 ft (32 sqft per sheet) for residential. 4×10 and 4×12 ft sheets are used for taller walls and reduce joint count but are harder to maneuver. The metric standard is 1.2 × 2.4 m (2.88 sqm), used outside North America. Choose Custom for non-standard sizes.

Step 6: Adjust the waste slider. The default 10 percent covers cuts, accidental breakage, and matching damage during install. For complex rooms with many corners and openings, use 15 percent. For new construction with simple rectangular rooms, 5 percent is enough.

Step 7: Optionally enter price per sheet for a total material cost. Typical pricing: standard 1/2 inch drywall runs $10–18 per 4×8 sheet, moisture-resistant (greenboard) runs $15–25, and fire-rated 5/8 inch runs $18–30.

Step 8: Click Calculate. Results include the sheet count (rounded up), estimated screws, joint tape, and joint compound for a standard 3-coat finish, plus per-room breakdown and floor plan.

Drywall (also called sheetrock, gypsum board, plasterboard, or wallboard) is sold in flat panels of fixed dimensions. The math is simpler than wallpaper — drywall sheets can be cut freely and leftover pieces fit elsewhere on the same wall — but there are still real-world variables that move the count.

Sheet sizes vary regionally. In the United States, the standard residential sheet is 4 × 8 ft (32 sqft). Taller walls use 4 × 9, 4 × 10, or 4 × 12 ft sheets. Commercial work often uses 4 × 12 to minimize joint count. Outside North America, the standard is 1.2 × 2.4 m (about 2.88 sqm, or roughly equivalent to a 4×8 ft sheet). The thickness most commonly used for residential walls is 1/2 inch (12.7 mm). Ceilings and garages typically use 5/8 inch (15.9 mm) for sag resistance and fire rating.

Coverage formula is area-based, not strip-based. Unlike wallpaper, drywall has no pattern alignment — cuts from one sheet can be used elsewhere. So the math is: total wall area + ceiling area − doors − windows, times 1 plus your waste percentage, divided by sheet area, rounded up.

Waste accounts for cuts and breakage. The 10 percent default covers: corners (where sheets must be cut to fit), door and window openings (where the cut pieces are smaller than the next opening), accidental cracks during transport or install, and ending up with leftover pieces too small to use. Rooms with many corners, sloped ceilings, or stairwells need 15 percent. Simple rectangular new-construction rooms can use 5 percent.

Multi-room sums conservatively. This calculator adds per-room areas before computing sheets, then applies waste once. That matches how a contractor would order — one delivery for the whole project — rather than treating each room as a separate purchase. Per-room breakdown shows what each room contributes.

Supplies estimates are industry rules-of-thumb. Screws: about 1 per sqft of finished area (16-inch stud spacing, screws every 12–16 inches along studs). Joint tape: about 0.5 linear ft per sqft of finished area (joints are roughly every 4 ft on 4×8 sheets, so the tape totals about half a foot per sqft of finish). Joint compound: about 0.005 gallons per sqft for a 3-coat finish (or about 1 five-gallon bucket per 1,000 sqft of finished area). These are estimates — exact figures depend on stud spacing, joint count, and finish quality (Level 1 to Level 5).

For each room with length L, width W, ceiling height H, doors D, windows N:

Wall area = 2 × (L + W) × H

Ceiling area = L × W (if including ceiling, otherwise 0)

Net area = Wall area + Ceiling area − (D × door area) − (N × window area)

(Default door area = 20 sqft / 1.86 sqm; default window area = 12 sqft / 1.11 sqm.)

Across all rooms:

Total area with waste = sum of net areas × (1 + waste %)

Sheet area = sheet length × sheet width (e.g., 4 × 8 = 32 sqft, or 1.2 × 2.4 = 2.88 sqm)

Sheets needed = ⌈Total area with waste / Sheet area⌉ (rounded up — partial sheets cannot be purchased)

Estimated supplies (industry rules-of-thumb):
- Screws ≈ 1 per sqft of finished area (or 10.76 per sqm)
- Joint tape ≈ 0.5 linear ft per sqft (or 0.5 m per sqm)
- Joint compound ≈ 0.005 gallons per sqft for 3-coat finish (or 0.2 L per sqm)

Example: 12 × 12 × 8 ft bedroom + ceiling, 1 door, 2 windows, 4×8 ft sheets, 10% waste.
- Wall area = 384 sqft, Ceiling = 144 sqft, Total = 528 sqft
- Net = 528 − 20 − 24 = 484 sqft
- With waste = 484 × 1.10 = 532.4 sqft
- Sheets = ⌈532.4 / 32⌉ = ⌈16.64⌉ = 17 sheets

Example 1: 10 × 10 room. 10 × 10 × 8 ft, 1 door, 2 windows, walls + ceiling. Wall = 320 sqft, ceiling = 100 sqft, total = 420 sqft. Net = 420 − 20 − 24 = 376 sqft. With 10% waste = 413.6. Sheets = ⌈413.6 / 32⌉ = 13 sheets at 4×8 ft.

Example 2: 1,200 sqft of drywall. Total area to cover = 1,200 sqft. With 10% waste = 1,320 sqft. Sheets = ⌈1,320 / 32⌉ = 42 sheets at 4×8 ft. Or 30 sheets at 4×12 ft (1,320 / 48 = 27.5 → 28 actually). Larger sheets reduce count and joint labor.

Example 3: 3,000 sqft house. A 3,000 sqft floor area typically has 2.5 to 3.5× as much drywall area (walls + ceilings) — roughly 7,500 to 10,500 sqft. With 10% waste, that's 8,250 to 11,550 sqft. At 32 sqft per 4×8 sheet, plan on 260 to 360 sheets depending on layout complexity, ceiling heights, and openings. Use the calculator with each room entered for precision.

Order 4×12 sheets when walls are long. Larger sheets reduce the number of joints, which means less tape, less compound, less sanding, and a flatter wall. The tradeoff: 4×12 sheets weigh about 80 lb each and need two people to maneuver. For DIY, stick to 4×8 unless you have a helper.

Buy 10 percent extra for residential rooms. This covers cuts around openings, accidental breakage during transport, and pieces that end up too small to use. New-construction rectangular rooms with few openings can use 5 percent. Stairwells, vaulted ceilings, and rooms with many corners need 15 percent.

Use 5/8 inch on ceilings and 1/2 inch on walls. Thicker 5/8 inch ceiling board resists sag and provides better fire and sound performance. 1/2 inch is standard for residential walls. Bathrooms and laundry rooms should use moisture-resistant (greenboard or purple) drywall, which costs about 50 percent more.

Match the joint compound to the job. Setting-type compound (sometimes called "hot mud") cures by chemical reaction and is necessary for the first coat on tape joints — it does not shrink. Pre-mixed (lightweight) compound is used for second and third coats — it sands easier but shrinks slightly. Most projects use both types.

Plan your sheet orientation. Hanging sheets horizontally (long edge across studs) is faster, has fewer joints, and gives a flatter final surface than vertical orientation. Horizontal hanging is standard practice in the US for residential work.

Allow drying time between coats. Joint compound takes 24 hours per coat to fully cure before sanding and the next coat. A typical 3-coat finish is a 3-to-5 day process, not counting the initial hang day. Rushing leads to cracks and uneven surfaces.

Sand carefully — wear a respirator. Drywall dust is fine and irritating. A dust mask is not enough — use a proper N95 respirator and seal off the work area. A pole sander or sanding sponge gives better results than a hand sanding block.