How many sheets of drywall do I need for a 12x12 room?

With 8 ft walls, one door and one window, the walls are 348 square feet after openings and the ceiling is 144, for 492 square feet. Adding 10% waste gives 541.2 square feet. That's 17 sheets of 4x8 drywall, or 12 sheets of 4x12.

How many square feet are in a sheet of drywall?

A 4x8 sheet is 32 square feet, a 4x10 is 40 and a 4x12 is 48. Divide the area you're covering, plus waste, by the sheet's square footage and round up to whole sheets.

How much extra drywall should I buy?

10–15% is a common allowance, not a rule. Use the low end for simple rectangular rooms hung with long sheets, and the high end for rooms with many corners, soffits, angled ceilings or openings, where more pieces are cut and offcuts are too small to use.

Should I use 4x8 or 4x12 drywall sheets?

Longer sheets mean fewer end joints to tape and finish, so 4x12 sheets often save finishing time on long walls and ceilings. They're heavier and harder to carry up stairs and through doors. 4x8 sheets are easier to handle alone and fit in more vehicles.

Do you subtract doors and windows when estimating drywall?

Usually yes for doors, which are full-height gaps in the wall. For windows, estimators differ: some deduct them, some deduct only large ones, because the board is often hung over the window and cut out, and that piece becomes waste. This calculator deducts both; raise the waste allowance if you hang over windows.

Free calculator

Drywall Calculator: How Many Sheets Do I Need?

Free drywall calculator: sheets for walls and ceilings in 4x8, 4x10 or 4x12, with waste and openings taken out.

Rooms

Length
ft
Width
ft
Height
ft
Doors
Windows
Length
ft
Width
ft
Height
ft
Doors
Windows

Include ceilings

Sheet size

Waste

10–15% is a common allowance.

Result

Sheets of drywall

32sheets

1,024 sq ft of board in 4 × 8 ft sheets

Walls, before openings: 720 sq ft
Doors and windows: −72 sq ft
Ceilings: 254 sq ft
Area to cover: 902 sq ft
With 10% waste: 992 sq ft

Openings use 21 sq ft per door and 15 sq ft per window. Longer sheets mean fewer joints to tape but are heavier to hang.

How it's calculated

Sheets = (wall area + ceiling area − openings) × (1 + waste %) ÷ sheet size, rounded up. A 12 × 12 ft room with 8 ft walls, one door and one window: 348 sq ft of wall + 144 sq ft of ceiling = 492 sq ft; × 1.10 = 541.2 sq ft; ÷ 32 = 16.9, so 17 sheets of 4×8.

How to use the drywall calculator

Add each room with its length, width and wall height, and count the doors and windows. Leave Include ceilings on if the ceilings are being hung too. Pick the sheet size and a waste allowance. The calculator works out wall area as perimeter × height, subtracts 21 sq ft per door and 15 sq ft per window, adds the ceilings, applies waste and divides by the sheet size.

Sheets for common room sizes

8 ft walls, ceiling included, one door and one window, 10% waste:

Room	Walls + ceiling	With 10% waste	4×8 sheets	4×12 sheets
10 × 10 ft	384 sq ft	422.4 sq ft	14	9
12 × 12 ft	492 sq ft	541.2 sq ft	17	12
12 × 14 ft	548 sq ft	602.8 sq ft	19	13
14 × 16 ft	668 sq ft	734.8 sq ft	23	16
15 × 20 ft	824 sq ft	906.4 sq ft	29	19

Sheet sizes and thickness

Sheet	Area	Typical use
4 × 8 ft	32 sq ft	Easiest to carry and hang alone; small rooms and repairs.
4 × 10 ft	40 sq ft	Walls up to 10 ft high hung vertically, with no end joint.
4 × 12 ft	48 sq ft	Long walls and ceilings; fewer joints to tape.

Half-inch board is the usual choice for interior walls. Five-eighths-inch board is common on ceilings, where it sags less between framing, and where fire-rated board is required by code. Bathrooms and other damp areas often get moisture-resistant board. Check what your local code and inspector require.

What to include

Closets, soffits and bulkheads: each adds wall or ceiling area that's easy to forget.
Both faces of new interior walls, if both sides are being hung.
Stairwell walls, measured as a rectangle plus a triangle along the stair.
Garage walls and ceilings as their own rooms, since they may need a different board.

Hanging direction and waste

On 8 ft walls, sheets are often hung horizontally: two 4 ft rows cover the height exactly, and the long edges (tapered for easy finishing) meet in the middle of the wall. On taller walls, the leftover strip at the top or bottom adds to waste. The 10–15% allowance covers those strips, cutouts for outlets and openings, and the odd broken corner. Remember to add tape, joint compound, screws and corner bead to the order.

For a full house, measuring every room is most of the work. FloorFigures measures each room from the floor plan, free, and gives wall area less openings, ceiling area and drywall sheets per room. The drywall guide walks through a whole-house example.

Updated October 12, 2026 · FloorFigures

Questions

How many sheets of drywall do I need for a 12x12 room?: With 8 ft walls, one door and one window, the walls are 348 square feet after openings and the ceiling is 144, for 492 square feet. Adding 10% waste gives 541.2 square feet. That's 17 sheets of 4x8 drywall, or 12 sheets of 4x12.
How many square feet are in a sheet of drywall?: A 4x8 sheet is 32 square feet, a 4x10 is 40 and a 4x12 is 48. Divide the area you're covering, plus waste, by the sheet's square footage and round up to whole sheets.
How much extra drywall should I buy?: 10–15% is a common allowance, not a rule. Use the low end for simple rectangular rooms hung with long sheets, and the high end for rooms with many corners, soffits, angled ceilings or openings, where more pieces are cut and offcuts are too small to use.
Should I use 4x8 or 4x12 drywall sheets?: Longer sheets mean fewer end joints to tape and finish, so 4x12 sheets often save finishing time on long walls and ceilings. They're heavier and harder to carry up stairs and through doors. 4x8 sheets are easier to handle alone and fit in more vehicles.
Do you subtract doors and windows when estimating drywall?: Usually yes for doors, which are full-height gaps in the wall. For windows, estimators differ: some deduct them, some deduct only large ones, because the board is often hung over the window and cut out, and that piece becomes waste. This calculator deducts both; raise the waste allowance if you hang over windows.

Skip the typing. Measure the plan.

Open the floor plan in FloorFigures and every room is measured for you, with the same math per room. Try it free on a sample plan; nothing is uploaded.