Drywall calculator: how many sheets do you need?

How many sheets of drywall for a 12x12 room?

A 12 ft by 12 ft room with 8 ft walls has 2 x (12 + 12) x 8 = 384 sq ft of wall. That's 12 sheets of 4 x 8 before waste.

Take out one 3 ft by 6 ft 8 in door (20 sq ft) and one 3 ft by 4 ft window (12 sq ft) and 352 sq ft is left. Add ten percent for waste and it's 387.2 sq ft, or 12.10 sheets, so you buy 13.

A room with gable ends gets its triangles added too. Two gable ends 12 ft wide and 4 ft high add 48 sq ft to the bare room, which then takes 14 sheets of 4 x 8 before waste.

Should you buy 4x8 or 4x12 sheets?

The page shows every size at once. For the same room with a door and a window at ten percent:

Sheet	4 x 8	4 x 9	4 x 10	4 x 12	4 x 14	4 x 16
Sheets	13	11	10	9	7	7

Bigger sheets mean fewer seams to tape, but they're heavier to lift. Hung horizontally on 8 ft walls, 4 x 12 sheets leave no butt joints on 12 ft walls.

Horizontal or vertical: how many seams?

On this page the sheet count stays the same whichever way you hang, but the seams change. The page counts each place two sheets meet.

In the 12 x 12 room with 8 ft walls and 4 x 8 sheets, hanging horizontally gives 4 flat seams (48 ft) and 8 butt joints (32 ft). Hanging vertically gives 8 flat seams (64 ft) and no butt joints. Butt joints are where two sheet ends meet, so the page counts them apart from the flat seams along the long edges.

How much mud, tape and how many screws?

The page uses the CertainTeed estimator's rates on the area you're covering: 1.25 screws and 0.37 ft of tape per sq ft, and 1 gallon of ready-mixed compound per 100 sq ft.

For the bare 12 x 12 room (384 sq ft), that's 480 screws, 3.84 gallons of compound and 142.08 ft of tape, which the page rounds up to 143 ft. It then shows each quantity before it's rounded to packs, then the packs: 1 pail of 4.5 gallons and 1 roll of 250 ft. Pick a smaller pail or roll and the pack count changes. The quantity doesn't.

The page assumes 8 ft sticks of corner bead, our starting figure, so each outside corner on a wall up to 8 ft tall takes one stick and a 10 ft wall takes two.

How much drywall for a bedroom with the ceiling?

Take an 11 ft by 14 ft bedroom with 8 ft walls, one door and two windows, and tick Include ceiling. Pick 4 x 12 sheets.

The walls are 2 x (14 + 11) x 8 = 400 sq ft. The ceiling is 14 x 11 = 154 sq ft. The door is 20 sq ft and each window 12, so 44 sq ft comes out. That leaves 510 sq ft to cover.

Add ten percent and it's 561 sq ft. Divide by 48 sq ft a sheet and you get 11.69, so you buy 12 sheets of 4 x 12. In 4 x 8 it's 18.

The rest comes off the 510 sq ft: 638 screws, 5.10 gallons of compound and 189 ft of tape. That's 2 pails of 4.5 gallons and 1 roll of 250 ft.

Hung horizontally, the walls get 4 flat seams (50 ft) and 4 butt joints (16 ft), because a 4 x 12 sheet covers an 11 ft wall in one piece but a 14 ft wall needs a join in each row. Hung vertically, they get 10 flat seams (80 ft) and no butt joints. The seam count covers walls only; the page doesn't lay out the ceiling.

How many sheets for a basement with 9 ft walls?

A 24 ft by 20 ft basement room with 9 ft walls, one door, two windows and two outside corners. No ceiling. Pick 4 x 9 sheets.

The walls are 2 x (24 + 20) x 9 = 792 sq ft. Take out 44 sq ft of openings and 748 sq ft is left. With ten percent that's 822.8 sq ft, or 22.86 sheets of 36 sq ft, so you buy 23. In 4 x 8 it's 26.

Screws come to 935, compound to 7.48 gallons and tape to 277 ft. That's 2 pails of 4.5 gallons and 2 rolls of 250 ft.

Here the hanging direction matters more. A 9 ft wall hung sideways with 4 ft wide sheets takes two full rows and a 1 ft strip, so each wall gets two flat seams. That's 8 flat seams (176 ft) and 24 butt joints (72 ft), 248 ft in all. Hung vertically, a 4 x 9 sheet runs floor to ceiling: 18 flat seams (162 ft) and no butt joints.

Each outside corner is 9 ft tall, so it takes two 8 ft sticks of bead. Two corners, 4 sticks.

Check it by hand

The page works in this order. You can follow it with a pencil.

1. Walls: 2 x (length + width) x height. Add length x width if the ceiling is in, and each gable's base x rise / 2.
2. Take out openings: each door is 36 x 80 in (20 sq ft) and each window 36 x 48 in (12 sq ft) unless you change them, plus any other openings you enter.
3. Sheets: net area x 1.10, divided by the sheet's area (32 for 4 x 8, 36 for 4 x 9, 48 for 4 x 12), then round up once.
4. Screws: net area x 1.25, rounded up.
5. Compound: net area / 100 gallons.
6. Tape: net area x 0.37 ft, rounded up to the next foot.

The basement, line by line: 2 x (24 + 20) x 9 = 792. Less 1 x 20 and 2 x 12 = 748. Then 748 x 1.10 = 822.8, and 822.8 / 36 = 22.86, up to 23 sheets. Screws: 748 x 1.25 = 935. Compound: 748 / 100 = 7.48 gal. Tape: 748 x 0.37 = 276.76, up to 277 ft. The Show your work panel under the result prints the same figures.

Why waste goes on the sheets but not the mud

Waste covers offcuts, and offcuts are board. So the page adds it to the sheet count and nowhere else. Screws, compound and tape follow the area you actually cover, which is the net area. That's why the basement's 935 screws come from 748 sq ft, not 822.8.

Ten percent is our starting figure, not a maker's. CertainTeed and Action Gypsum both print a panel count with no waste in it: 1,000 sq ft gives 32 sheets of 4 x 8 on both, which is 31.25 rounded up. The same 1,000 sq ft on this page, with no openings, gives 35.

How quantities turn into pails and rolls

Round in this order, or you'll overbuy:

• Sheets are sold singly, so the count is rounded once, after waste.
• Tape is rounded up to the next foot, then into rolls. The bedroom's 189 ft is 1 roll of 250 ft, or 3 rolls of 75 ft.
• Compound isn't rounded until it becomes pails. The basement's 7.48 gallons is 2 pails of 4.5 gallons, or 3 pails of 3.5. The bedroom's 5.10 gallons is 6 pails of 1 gallon.
• Corner bead is counted per corner, in 8 ft sticks.

Change the pail or roll size and only the pack count moves. The gallons and feet stay put.

Where the figures come from

• Screws 1.25 per sq ft, tape 0.37 ft per sq ft, ready-to-use compound 1 gallon per 100 sq ft: CertainTeed Drywall Calculator, certainteed.com/drywall-calculator, read 24 Oct 2026. At 1,000 sq ft it prints 1,250 screws, 370 ft of tape and 10 gallons. Confirmed 24 Oct 2026 at certainteed.com/drywall-calculator?area=1000 (the figures sit in collapsed sections): "Drywall Screws: 1,250 Screws", "Total joint tape required: 370 feet", "Ready-to-Use Compounds: 10 Gallons", and "Do not subtract for openings like doors, windows or outlets."
• The same 1,250 screws, 370 ft of tape and 10 gallons of lightweight all purpose compound at 1,000 sq ft: Action Gypsum Supply Drywall Calculator, actiongypsum.com/drywall-calculator/, read 24 Oct 2026.
• Ten percent waste, the 36 x 80 in door, the 36 x 48 in window, the 8 ft bead stick and the 1 and 3.5 gallon pails are our starting figures, not sourced ones.

What this doesn't do

It works by area, not sheet by sheet, so it doesn't plan where each sheet goes or reuse offcuts. Seams are counted on walls only, not the ceiling. It doesn't recommend board thickness, fire-rated board or fastener spacing, and it doesn't work out compound by finish level. It doesn't count nails, setting-type compound, primer or adhesive. It doesn't handle sloped or vaulted ceilings, and it doesn't look up prices.

Before you buy

Decide whether to take out doors and windows. CertainTeed's tip is not to, and to measure the whole wall. The page takes them out by default. In the 12 x 12 room that's 13 sheets with one door and one window taken out, or 14 with none. Set doors and windows to 0 if you'd rather follow the maker. Then check board thickness and any fire-rated wall, such as a garage wall, with your local building department.

Drywall calculator FAQ

Related tools

To pick a waste allowance for cuts, see how much waste to add. More material calculators are on the home projects page.