Drywall Calculator
Enter a room and get the number of drywall sheets it takes, with doors and windows deducted, plus the screws, joint compound and tape that go with them.
Drywall sheets you need
365 sq ft of net surface, 10 % waste included.
- Net surface
- 365 sq ft
- Screws
- 4161 1/4 in coarse thread
- Joint compound
- 1 bucket3.7 gal, 4.5 gal each
- Joint tape
- 1 roll146 ft needed
The numbers above are a worked example for a 14 ft x 12 ft room with 8 ft ceilings, one door and two windows. Allow this page to run scripts in your browser to use your own numbers, or follow the formula below and do it by hand.
How the drywall calculator works, step by step
Estimating drywall is a surface-area problem, not a volume problem. You find the area of everything you intend to board, subtract the holes you are not boarding, add a waste allowance, and divide by the area of one sheet.
Using the perimeter is what makes this quick. You do not need to measure four walls separately unless the room is not rectangular.
Worked example: a 14 ft x 12 ft bedroom, 8 ft ceilings, one door, two windows
- Perimeter: 2 x (14 + 12) = 52 ft
- Wall area: 52 x 8 = 416 sq ft
- Openings: 1 door at 21 + 2 windows at 15 = 51 sq ft
- Net area: 416 - 51 = 365 sq ft
- With 10 % waste: 365 x 1.10 = 401.5 sq ft
- Sheets: 401.5 / 32 = 12.5, rounded up to 13 sheets
Board the ceiling too and you add 14 x 12 = 168 sq ft, which takes the job to 19 sheets. The ceiling is nearly half the material in a small room, which is why it is a separate checkbox and not an assumption.
Which sheet length should you buy?
Sheet width is always 4 ft in the United States. Length is the choice, and it is a real one: fewer, longer sheets mean fewer butt joints, and butt joints are the seams that show under raking light because they have no factory taper.
| Sheet | Area | Weight, 1/2 in | Best for |
|---|---|---|---|
| 4 ft x 8 ft | 32 sq ft | about 52 lb | Standard 8 ft walls, tight stairwells, working alone |
| 4 ft x 10 ft | 40 sq ft | about 65 lb | Rooms 10 ft across, fewer seams |
| 4 ft x 12 ft | 48 sq ft | about 78 lb | Long walls and ceilings, fewest butt joints |
Panel dimensions per USG, Sheetrock Brand Gypsum Panels product page - product page. Weights are approximate and vary between standard and lightweight panels; check the panel you buy if weight matters for handling.
A practical rule: pick the sheet length that spans your wall in one piece if you can carry it. A 12 ft wall boarded horizontally with one 4 ft x 12 ft sheet top and bottom has zero butt joints. The same wall in 8 ft sheets has one, and you will be feathering that joint out three feet wide to hide it.
Thickness
Thickness does not change the sheet count, only the product you buy. Half inch is the standard for walls. Five-eighths is used for ceilings on 24 in framing to resist sag, and for fire-rated assemblies. Quarter inch is for laminating over an existing surface or bending around a curve. If a code official has specified a rated assembly, the thickness and panel type are not yours to choose.
Screws, mud and tape
Screws
Fastener spacing follows the framing. On walls with studs at 16 in on center and screws every 12 in along each stud, a 4 ft x 8 ft sheet takes about 32 screws. Ceilings take more, around 40 per sheet, because gravity is working against the panel all day. As a sanity check, roughly one screw per square foot of board is the number most estimators carry in their head.
Buy 1 1/4 in coarse-thread screws for wood framing and 1 1/4 in fine-thread for steel studs. They are not interchangeable: coarse threads strip out in metal.
Joint compound
That figure covers a standard three-coat, Level 4 finish: a tape coat, a fill coat and a finish coat over the seams, plus the fastener heads and the inside corners. It works out to roughly one 4.5 gallon bucket per 450 sq ft of board. Two things push it up: a Level 5 skim coat over the whole surface, which can double the compound, and a job with many small pieces, because compound follows seams and small pieces mean more seams per square foot.
Tape
Paper tape is the default and is stronger in a flat seam. Fiberglass mesh is faster and is normally paired with a setting-type compound. Either way the length needed scales with seams, and seams scale with area, which is why the estimate is expressed per square foot.
Compound, tape and fastener quantities cross-checked against Lowe's Drywall Materials Estimator - estimator sheet. Coverage varies with finish level and technique; these are planning figures, not a guarantee.
Corner bead
Corner bead is not in the calculator because it is a linear measurement that does not scale with area. Count your outside corners, multiply by the ceiling height, and add a stick for each one. It is sold in 8 ft and 10 ft lengths, and you want one piece per corner, not two pieces spliced.
Cases the simple formula does not cover
Rooms that are not rectangles
The perimeter method needs a closed rectangle. For an L-shaped room, measure each wall run, add the lengths to get the true perimeter, and multiply by the ceiling height. For the ceiling area, split the shape into rectangles and add them up. Then switch this calculator to total square footage.
Cathedral and sloped ceilings
A gable wall under a sloped ceiling is a rectangle plus a triangle: rectangle at the low wall height, triangle of (width x rise) / 2 on top. The sloped ceiling itself is longer than its horizontal projection, so measure along the slope, not across the floor. Skipping this is the most common way a drywall order comes up short.
Should you deduct small openings?
Deduct doors and full windows. Do not deduct outlets, switches, recessed lights or a single small transom: you cut the hole out of a full sheet and the cut-out is scrap. Some estimators do not deduct anything under about 20 sq ft, on the grounds that the offcut around a small window is rarely usable elsewhere. If you prefer that approach, set the window count to zero and keep the 10 % waste.
Garages, basements and fire separation
Attached-garage ceilings and walls shared with living space, and some basement assemblies, are usually required to be fire rated, which means a specific panel type and thickness, and sometimes two layers. Two layers doubles the sheet count and the screws, but not the tape and compound on the base layer. Check the requirement with your local building department before ordering.
Frequently asked questions
How many sheets of drywall do I need for a 12x12 room?
A 12 ft x 12 ft room with 8 ft ceilings has a 48 ft perimeter and 384 sq ft of wall. Deduct one door and one window, about 36 sq ft, for 348 sq ft net. With 10 % waste that is 383 sq ft, which is 12 sheets of 4 ft x 8 ft. Add the ceiling, another 144 sq ft, and it goes to 17 sheets.
How do I calculate drywall sheets from square footage?
Divide the net square footage by the area of one sheet and round up: 32 sq ft for 4 ft x 8 ft, 40 for 4 ft x 10 ft, 48 for 4 ft x 12 ft. Add a waste allowance first, normally 10 % for a plain rectangular room and 15 % where there are many corners, soffits or angled cuts.
How much joint compound do I need per sheet of drywall?
Roughly 0.32 gallons per 4 ft x 8 ft sheet for a three-coat Level 4 finish, which comes from 0.01 gallons per square foot. In bucket terms, one 4.5 gallon bucket does about fourteen sheets. A full Level 5 skim coat can double that.
How many screws per sheet of drywall?
About 32 per 4 ft x 8 ft sheet on walls with framing at 16 in on center, and about 40 on ceilings. Longer sheets take proportionally more. A useful shortcut when buying: about one screw per square foot of board, then round up to the next box.
Do I subtract windows and doors when estimating drywall?
Yes for full door and window openings, because those are large areas of board you genuinely do not hang. No for outlets, switches and recessed lights, because the cut-outs come out of full sheets and the pieces are scrap. This calculator lets you set both the count and the area per opening so you can match your own openings rather than a generic assumption.
Should drywall be hung horizontally or vertically?
It does not change the sheet count, only the seam pattern. Horizontal hanging on 8 ft walls puts the tapered seam at a comfortable working height and produces fewer linear feet of joint, which is why it is standard in residential work. Vertical hanging is common in commercial work and where a fire rating specifies it.
How much waste should I allow for drywall?
Ten percent for a straightforward rectangular room. Fifteen percent when the space has soffits, bulkheads, closets, angled walls or a lot of small cuts. Working with 4 ft x 12 ft sheets in a small room also raises waste, because the offcuts are large and often unusable.