CalcLibrary

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.

Units
m
m
m
%
Examples

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

Sheets to Buy
12 sheets
Base drywall area
31.2 m²
Waste area
3.12 m²
Area with waste
34.32 m²
Sheet area purchased
34.56 m²
Wall Area
31.2 m²
Ceiling Area
0 m²

Buy 12 sheets — 10% waste already included.

Estimate before openings. Subtract doors and windows manually for a tighter count, or rely on the waste allowance to absorb them.

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Examples

How It Works

Formula

Aw=2(L+W) HA_w = 2(L + W)\,H

Ac={L⋅Wif ceiling included0otherwiseA_c = \begin{cases} L \cdot W & \text{if ceiling included} \\ 0 & \text{otherwise} \end{cases}

A=Aw+AcA = A_w + A_c

N=⌈AAs⋅(1+w100)⌉N = \left\lceil \frac{A}{A_s} \cdot \left(1 + \frac{w}{100}\right) \right\rceil

Variables

LL

Room length(m)

WW

Room width(m)

HH

Ceiling height(m)

AwA_w

Wall area (perimeter × height)(m²)

AcA_c

Ceiling area (zero if not included)(m²)

AA

Total drywall area(m²)

AsA_s

Area of one sheet(m²)

ww

Waste allowance(%)

NN

Sheets to buy (rounded up)

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.

Frequently Asked Questions

01Should 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.
02What 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.
03Which 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.
04What 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.
05Does 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.

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