Home › Drywall Calculator › This size

How Many Sheets of Drywall for a 12×24 ft Room with a 9 ft Ceiling?

A 12 by 24 foot room with a 9 foot ceiling needs this many 4×8 drywall sheets, with mud, tape and screws worked out. Here is the answer, plus a calculator you can adjust if your measurements are slightly different.

Answer: 21 sheets

How it changes with ceiling height

Same area, different ceiling height:

Ceiling height	8	9	10
Drywall sheets needed	19 sheets	21 sheets	23 sheets
Gross wall area	576 ft²	648 ft²	720 ft²

What a 12×24 ft room with a 9 ft ceiling actually involves

At 597 ft² this is a solid two-person job. 21 sheets at 4 ft × 8 ft weigh roughly 1,155 lb in total, and a full sheet is awkward for one person on a ceiling or above shoulder height. Budget two days: hang on the first, tape and coat on the second.

The room has 72 ft of wall around 648 ft² of gross surface. Knock off 51 ft² for openings and you are boarding 597 ft², or 657 ft² once your 10 percent waste allowance is added. That is 21 sheets of 4 ft × 8 ft board.

Deducting 1 door and 2 windows removes 51 ft², or 8 percent of the wall. That is about 2 sheets you do not buy. Cutting openings out of a hung sheet wastes the offcut, which is exactly what the waste allowance in this calculator is for — do not set it to zero and expect the cuts to come out even.

A 9 ft ceiling leaves a 12 in strip along the top once two 4 ft courses are hung. It is the classic 9 ft problem. Cut the strip from the last sheet of each course, keep the offcut for the next wall, and stagger the joints so no rip lines up with the one behind it. The alternative is hanging 4 ft × 12 ft sheets vertically — full height in one piece with no rip, at the cost of cutting 3 ft off every sheet.

Where the square footage goes

Measured as	Amount	How it is worked out
Perimeter	72 ft	12 ft + 24 ft, doubled
Gross wall area	648 ft²	72 ft × 9 ft ceiling
Doors deducted	21 ft²	1 × 21 ft²
Windows deducted	30 ft²	2 × 15 ft²
Net area to board	597 ft²	gross minus openings
With 10% waste	657 ft²	the figure to buy against
4 ft × 8 ft sheets	21 sheets	657 ft² ÷ 32
4 ft × 12 ft sheets	14 sheets	657 ft² ÷ 48
Ceiling, if you board it	9 more sheets	12 × 24 = 288 ft², no openings to deduct

At 12 ft × 24 ft you have two 24 ft runs and two 12 ft runs. Board the long walls first and keep the offcuts — they are usually the right length for the short walls, which is where a 20 percent saving on sheet count comes from.

Wall by wall

4 ft × 8 ft sheets hung horizontally, at a 9 ft ceiling, divide into 3 courses per wall:

Wall run	Surface	Pieces at 4 ft × 8 ft
2 × 12 ft wall	216 ft²	2 sheets per course × 3 = 6 per wall, 12 in total
2 × 24 ft wall	432 ft²	3 sheets per course × 3 = 9 per wall, 18 in total

Those are pieces, not sheets. Laid out literally the walls would take 30 pieces, against the 21 sheets you actually buy — the gap is the 0 ft offcut that comes off every 24 ft run and finishes the next course. It is the biggest saving available on a room this size, and it only works if you cut the long walls first and keep the offcuts.

At 24 ft by 12 ft this is a long, narrow room — a corridor, a galley kitchen or a single garage. The two long walls dominate the board count and the two ends are barely wider than one sheet, so most of your offcuts come from the long runs. Cut the ends from long-run offcuts wherever the lengths match and this room boards cheaper than its area suggests.

A 24 ft run takes 3 sheets per course and leaves 0 ft of offcut every time. The 24 ft runs take 3 each and leave 0 ft — which is the piece that usually finishes the ends without touching another full sheet.

Mud, tape and screws

Item	Quantity	Rule of thumb
Joint compound	2 gal	about 1 gal per 300 ft² for a level 4 finish
Joint tape	2 rolls	a 500 ft roll per 500 ft² of board
Drywall screws	723	about 1.1 per ft², roughly 32 per 4×8 sheet
Studs, if reframing	64	1 per ft at 16 in centres, plus 4 for corners and 2 per opening
Corner bead	as needed	one length per outside corner, inside and outside

Buy the mud in the largest tub that stays workable. A 2 gal job is 1 standard 4.5 gal bucket, and once a bucket is opened it skins over within days — powder you mix yourself keeps indefinitely and is cheaper per gallon on a job this size. Coat thin and build up: three thin passes sand far easier than two thick ones, and every extra pass costs you sanding time, not just mud.

How to hang it

Mark and check the studs. Board goes across them, so it does not matter if the spacing wanders — but it does matter that you can find them after the board is up.
Start at the top with a full 4 ft course, then the next full course, and finish with the 12 in rip at the bottom where it is easy to scribe to the floor.
Stagger the vertical joints. A joint that lines up with the one on the other side of a stud is the one that cracks first.
Keep the board about 1/2 in off a concrete floor and tight to the ceiling. Movement happens at the floor line, not at the ceiling.
Screw about 12 in apart in the field and every 8 in on the edges, driving the heads just below the surface without breaking the paper. A screw that tears the paper holds nothing.
Leave a 1/8 in gap at butt joints and fill it with mud before taping. Boards that are jammed tight buckle at the seam.
This room needs 21 sheets and roughly 723 screws. Order the sheets and the screws together — a shortfall of 20 screws is a wasted trip.

Which board to buy

1/2 in board is the default for walls and is what the count above assumes. Step up to 5/8 in for ceilings and for bedrooms where you want the room to feel quieter; it sags less at 24 in centres and takes screws better, at about 20 percent more weight per sheet. Use 1/4 in only for curves. For bathrooms, laundry rooms and basements use moisture-resistant board — it is not waterproof, and it still needs a proper waterproofing layer behind a tiled shower. Board that is going to sit in a garage or a shed is worth buying in 5/8 in for the impact resistance alone.

Common questions

How many sheets of drywall for a 12×24 ft room with a 9 ft ceiling?

21 sheets of 4 ft × 8 ft board, or 14 if you buy 4 ft × 12 ft sheets. The walls come to 597 ft² after deducting 1 door and 2 windows, and 657 ft² with your 10 percent waste allowance.

Do I need to add the ceiling?

Only if you are boarding it. The ceiling here is 288 ft², which is 9 more 4 ft × 8 ft sheets, roughly 48 percent on top of the walls. Ceilings take longer per sheet than walls — everything is overhead — so treat it as separate work, not extra work.

How do I hang drywall on a 9 ft ceiling?

Two full 4 ft courses plus a 12 in rip. Put the rip at the floor where it is easy to scribe, or at the top if the ceiling line is straight and the floor is not. Never put a narrow rip at the bottom on a floor that slopes.

How much joint compound and how many screws?

About 2 gallons of compound and 723 screws for this room, plus 2 rolls of tape. Buy a little more mud than the figure: a second coat always drinks more than the first, and running out mid-pass leaves a ridge you have to sand flat.

Should I hang drywall horizontally or vertically?

Horizontally, across the studs, unless you are using 4 ft × 12 ft sheets at a 9 ft ceiling. Horizontal hanging puts fewer joints in the middle of the wall, and every joint you can put at a height you can reach is a joint that is easier to finish. Vertical hanging is faster to put up and harder to finish.