Drywall Calculator

Estimate how many drywall sheets you need for a room. Enter room dimensions, ceiling height, sheet size, and waste allowance to get the total wall area, optional ceiling area, and the exact number of sheets to buy.

Examples

Small bedroom

A 3.5 m × 3 m bedroom with 2.4 m ceilings, walls only, EU 1200 × 2400 mm sheets, 10% waste.

Room Length: 11.483 ft
Room Width: 9.843 ft
Ceiling Height: 7.874 ft
Sheet Size: 1200 × 2400 mm (EU, 2.88 m²)
Waste Allowance: 10 %
Include Ceiling: No, walls only

Sheets to Buy

12 sheets

Base drywall area

335.83 ft²

Waste area

33.58 ft²

Area with waste

369.42 ft²

Sheet area purchased

372 ft²

Wall Area

335.83 ft²

Ceiling Area

0 ft²

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How It Works

Formula

A_w = 2(L + W)\,H

A_c = \begin{cases} L \cdot W & \text{if ceiling included} \\ 0 & \text{otherwise} \end{cases}

A = A_w + A_c

N = \left\lceil \frac{A}{A_s} \cdot \left(1 + \frac{w}{100}\right) \right\rceil

Variables, symbols and units

$L$: Room length(m)
$W$: Room width(m)
$H$: Ceiling height(m)
$A_w$: Wall area (perimeter × height)(m²)
$A_c$: Ceiling area (zero if not included)(m²)
$A$: Total drywall area(m²)
$A_s$: Area of one sheet(m²)
$w$: Waste allowance(%)
$N$: Sheets to buy (rounded up)

Calculation method explained

Enter room length, width, ceiling height, sheet size, and waste allowance. The calculator computes wall area as perimeter × height, optionally adds the ceiling, multiplies the total by (1 + waste %), divides by the sheet area, and rounds up to whole sheets.

References and source material

Examples

Small bedroom11.483 ft · 9.843 ft → 12 sheets

A 3.5 m × 3 m bedroom with 2.4 m ceilings, walls only, EU 1200 × 2400 mm sheets, 10% waste.

Room Length: 11.483 ft
Room Width: 9.843 ft
Ceiling Height: 7.874 ft
Sheet Size: 1200 × 2400 mm (EU, 2.88 m²)
Waste Allowance: 10 %
Include Ceiling: No, walls only

Sheets to Buy: 12 sheets

Garage19.685 ft · 22.966 ft → 24 sheets

A 6 m × 7 m garage with 2.4 m ceilings, walls only, EU 1200 × 2400 mm sheets, 10% waste.

Room Length: 19.685 ft
Room Width: 22.966 ft
Ceiling Height: 7.874 ft
Sheet Size: 1200 × 2400 mm (EU, 2.88 m²)
Waste Allowance: 10 %
Include Ceiling: No, walls only

Sheets to Buy: 24 sheets

Basement with ceiling26.247 ft · 32.808 ft → 64 sheets

An 8 m × 10 m basement with 2.4 m ceilings, walls + ceiling, EU 1200 × 2400 mm sheets, 10% waste.

Room Length: 26.247 ft
Room Width: 32.808 ft
Ceiling Height: 7.874 ft
Sheet Size: 1200 × 2400 mm (EU, 2.88 m²)
Waste Allowance: 10 %
Include Ceiling: Yes, walls + ceiling

Sheets to Buy: 64 sheets

Frequently Asked Questions

Should I subtract doors and windows?

For a quick estimate, no — the waste allowance usually absorbs them. For a tighter buy, subtract roughly 21 ft² (2 m²) per standard door and roughly 15 ft² (1.4 m²) per standard window from the wall area before counting sheets.

What waste allowance should I use?

10–15% is standard for a rectangular room with few openings. Bump to 15–20% if the layout is irregular, has many cutouts (windows, outlets, vents), or you are inexperienced with cutting drywall cleanly.

Which sheet size should I pick?

In the US, 4 × 8 ft is the default and easiest for one person to handle. 4 × 10 ft and 4 × 12 ft reduce horizontal seams on long walls but are heavier. In Europe, 1200 × 2400 mm is the equivalent default; 1200 × 3000 mm suits taller walls.

What thickness of drywall do I need?

1/2 in (12.5 mm) is the standard for interior walls. Use 5/8 in (15 mm) for ceilings, party walls, and any wall with a fire-rating requirement. Wet-area boards (green or blue) go in bathrooms and laundries.

Does this include screws, tape, and joint compound?

No — this calculator counts boards only. As a rough rule of thumb, allow about 30 screws per 4 × 8 ft sheet, one roll of paper or mesh tape per 7–10 sheets, and a 5-gallon bucket of joint compound per 12–15 sheets.

Drywall Calculator

Small bedroom

How It Works

Examples

Frequently Asked Questions

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