Drywall Sheet Calculator
Enter your room and get the number of sheets to buy — plus the screws, joint compound and tape you'll need to finish them. Add a section for each rectangle if the room is L-shaped.
Take this list to the store
We'll email the quantities above, what you typed in, and a link that reopens this calculator already filled in — so you can adjust it on your phone in the aisle.
How to work it out
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Measure each rectangle of the room
Measure the length and width of the floor. If the room is L-shaped or opens into an alcove, split it into rectangles and measure each one — the calculator adds them together. Measuring the floor rather than the walls is quicker and gives the same perimeter.
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Measure floor to ceiling
Measure in a corner, not a doorway. If the height varies by more than an inch across the room, use the largest figure — you can trim a sheet down, but you cannot stretch one.
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Count doors and windows
A standard interior door is about 21 sq ft and an average window about 12 sq ft. Only deduct them if you have several; on a small job it is safer to leave them in and keep the cut-offs for patching.
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Add waste and round up to whole sheets
Ten per cent covers normal cut-offs. Go to 15% if the room has lots of corners, angled walls or a stairwell, since those produce more unusable scrap. Drywall is only sold in whole sheets, so always round up.
Sheets needed by room size
Walls and ceiling, 8 ft high, one door and one window deducted, 10% waste, using 4 × 8 ft sheets.
| Room size | Area to cover | 4 × 8 sheets | 4 × 12 sheets |
|---|---|---|---|
| 8 × 10 ft | 335 sq ft | 12 | 8 |
| 10 × 10 ft | 387 sq ft | 14 | 9 |
| 10 × 12 ft | 439 sq ft | 16 | 11 |
| 12 × 12 ft | 495 sq ft | 18 | 12 |
| 12 × 14 ft | 551 sq ft | 19 | 13 |
| 12 × 16 ft | 607 sq ft | 21 | 14 |
| 14 × 16 ft | 671 sq ft | 24 | 16 |
| 16 × 20 ft | 863 sq ft | 30 | 20 |
Rounded up to whole sheets. Your own measurements always win over a table.
What each sheet size covers
| Sheet | Area | Weight (1/2 in.) | Best for |
|---|---|---|---|
| 4 × 8 ft | 32 sq ft | ~52 lb | Almost everything. One person can carry it. |
| 4 × 10 ft | 40 sq ft | ~65 lb | Walls over 8 ft, fewer horizontal joints. |
| 4 × 12 ft | 48 sq ft | ~78 lb | Long walls and ceilings. Needs two people. |
Weights are for standard 1/2 in. board. Moisture-resistant and Type X fire-rated sheets are heavier.
How many sheets of drywall for a 12x12 room?
A 12 × 12 ft room with an 8 ft ceiling has 384 sq ft of wall and 144 sq ft of ceiling. Take off one door and one window — about 33 sq ft — and you are covering 495 sq ft. Add 10% for waste and divide by 32, and you need 18 sheets of 4 × 8 drywall, or 12 sheets of 4 × 12.
Doing the walls only, without the ceiling, drops it to 13 sheets.
Do I need to deduct doors and windows?
On a single room, most contractors do not bother. The cut-offs around an opening are rarely reusable, and the leftover board is useful for patches. On a whole house the deduction is worth making — twelve doors and twenty windows is close to 500 sq ft, which is fifteen sheets you would otherwise be paying for and storing.
This calculator deducts them, then adds waste on top, which lands in a sensible place either way.
How much joint compound and tape will I need?
Budget about one gallon of all-purpose compound per 100 sq ft of drywall for taping plus two finish coats. A 4.5-gallon bucket covers roughly 450–475 sq ft, so an average bedroom takes one bucket with a little left over.
For tape, allow 40 ft per 100 sq ft of board. A 250 ft roll does about 625 sq ft. Paper tape is stronger at inside corners; mesh is easier for beginners on flat joints but needs setting-type compound over it.
Which thickness should you buy?
- 1/2 in. — the default for walls and for ceilings on joists at 16 in. centers.
- 5/8 in. — required for many garage and party walls, and better on ceilings at 24 in. centers because it sags less.
- 1/4 in. — for curves and for skinning over an existing wall, not for structure.
Check your local code before choosing anything thinner than 5/8 in. on a garage ceiling below living space.
How this is worked out
No black box — here is the arithmetic the calculator runs, so you can check it against your own numbers.
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perimeter = 2 × (length + width), summed over every sectionEach rectangle you enter contributes its own perimeter, which is how L-shaped rooms total correctly. -
wall area = perimeter × ceiling heightThe four walls, unrolled flat. -
+ ceiling area = length × widthOnly when you switch the ceiling on. -
− (doors × 21) − (windows × 12)Average opening sizes in square feet. -
× (1 + waste ÷ 100)Cut-offs around openings and corners that cannot be reused. -
÷ sheet area, rounded upDrywall is sold only in whole sheets. -
screws = sheets × 32, rounded to the next 100One every 12 in. on field studs, 8 in. on edges, at 16 in. spacing. -
compound = area ÷ 105 gallonsTaping plus two finish coats. -
tape = area × 0.4 ft, rounded to the next 50Roughly 40 linear feet of tape per 100 sq ft of board.
Common questions
How many sheets of drywall are in a bundle?
Drywall is usually sold as a pair of sheets banded face to face — that pair is a “bundle” or a “lift” at some yards. Larger orders come on a pallet of 40 to 50 sheets. Prices are almost always quoted per sheet, not per bundle.
How much does a sheet of drywall cover?
A 4 × 8 ft sheet covers 32 sq ft, a 4 × 10 covers 40 sq ft and a 4 × 12 covers 48 sq ft. That is the raw face area — it does not allow for cut-offs, which is why a waste percentage is added on top.
Should I hang drywall horizontally or vertically?
Horizontally on walls in homes: it puts the joint at a comfortable working height, uses fewer linear feet of tape and hides slightly bowed studs. Vertically is normal in commercial work and where fire ratings require joints over framing. Ceilings run perpendicular to the joists either way.
How many screws per sheet of drywall?
About 32 for a 4 × 8 wall sheet at 16 in. stud spacing — roughly one every 12 in. on intermediate studs and every 8 in. along the edges. Ceilings need more, around 40 per sheet. A 1 lb box holds about 180 screws of 1-1/4 in.
Does the calculator work for an L-shaped room?
Yes. Split the floor into rectangles, press “Add another section”, and enter each one. The perimeter and ceiling area are worked out for every section and added together, which is the part most calculators leave you to do on paper.
How much waste should I allow?
Ten per cent for a plain rectangular room. Fifteen per cent if there are lots of corners, angled ceilings, a stairwell, or many small openings — all of those turn full sheets into scrap faster than a straight wall does.
Is drywall the same as sheetrock?
Yes in everyday use. Sheetrock is a brand of drywall made by USG, in the same way that Hoover is a brand of vacuum. Plasterboard and wallboard are the same product under other names.
Can I just buy by square footage?
No — it is sold in whole sheets, so anything left over from a division has to be rounded up. Ordering 480 sq ft when you need 495 leaves you one sheet short and making a second trip, which is why this calculator rounds up automatically.
Where these figures come from
Every figure below is traceable. How we check the numbers explains how they are verified, and the coverage reference collects them all in one place.
- USG Sheetrock installation guide — sheet sizes, weights and fastener spacing
- Gypsum Association GA-216 — the standard for applying and finishing gypsum panels
- USG joint compound data sheets — coverage per bucket for taping and finish coats
- International Residential Code, chapter 7 — where 5/8 in. and Type X board are required
Think a number here is wrong? Tell us — we check every report, correct the page, and date the change. Last checked September 11, 2026.