How to use the drywall calculator
Add a room for each space you are hanging board in: its length, its width and its wall height, and a tick if the ceiling gets board too. Under each room list its doors and windows with their own sizes and how many of each. Pick the sheet size and thickness you plan to buy, then read the sheets to buy, the screws, the joint tape and the joint compound. Type your own prices and the page adds up the lines you priced. The One wall tab lays one wall out sheet by sheet with a cut list. Everything stays in your browser unless you make a share link.
How the sheets are counted
The page makes two counts and tells you to buy the larger. The area count adds up the board you need, takes off every opening, adds your waste percent and divides by the area of one sheet. The layout count hangs real sheets: it fills each wall course by course, starts every second course with a half sheet so the end joints stagger, and counts whole sheets, reusing a cut-off piece on the same wall when it is long enough. The layout hangs board across openings and cuts them out later, so it does not subtract them.
buy = the larger of the area count and the layout count
A worked example
A room 14 feet by 12 feet with 8-foot walls has 52 feet of wall, or 416 square feet. One 36 by 80 inch door takes off 20 square feet and two 36 by 48 inch windows take off 24 more, which leaves 372 square feet of wall. The ceiling adds 14 × 12 = 168, so the room needs 540 square feet of board. A 4 × 8 sheet covers 32 square feet, so 540 × 1.10 ÷ 32 is 18.6, which rounds up to 19 sheets. Hung sideways, the layout needs 20, so the page says buy 20. With 4 × 12 sheets the layout needs only 14. That example is what the calculator shows when it opens.
Screws
You choose how far apart the screws go, or leave the box empty to use the code maximum. The International Residential Code table for gypsum board (R702.3.5) lists the longest allowed spacing without adhesive: 12 inches on a ceiling, and on a wall 16 inches when the studs are 16 inches apart or 12 inches when they are 24 inches apart. The page counts the framing lines that cross each whole sheet and puts a screw every spacing along each line, ends included. A 4 × 8 sheet hung sideways on 16 inch studs at 16 inches takes 28 screws, and at 12 inches it takes 35. The count has no allowance for stripped screws.
Joint tape, compound and corner bead
Every sheet edge ends at another sheet or at a corner, so each sheet carries about half its perimeter in joints. For a 4 × 8 sheet that is 12 feet of tape per 32 square feet, or 0.375 feet per square foot. USG says to expect about two 4.5 gallon pails of its ready-mix all-purpose compound for 1,000 square feet of board, which the page scales to your area (9 gallons per 1,000 square feet). Other compounds differ, so treat it as a starting point. Corner bead is figured from the outside corners you type, one wall height each.
Which size and which direction
The table under the answer shows the layout count in each size, so you can see the fewest. Long sheets mean fewer end joints on a long wall, and an 8-foot wall hung up and down with 4 × 8 sheets has no horizontal joint. A 54-inch sheet covers a 9-foot wall in two courses. The Chart tab lists the weight of each size.
Where the numbers come from
Sheet weights are USG's nominal pounds per square foot: 1.2 for 1/4 inch, 1.4 for 3/8, 1.6 for 1/2 and 2.2 for 5/8 inch board (Sheetrock submittal sheet 09250), and 1.25 for UltraLight 1/2 inch. Other makers and types differ, so check the label. Screw spacing follows the IRC table described above; codes are adopted on different editions, and your building department decides which applies. Fire-rated walls, ceilings and shaft walls are built to a listed assembly that sets the board type, the layers, the fasteners and the joints, so follow the listing and not this page. This calculator does not size framing and is not a substitute for the local code. USG lists sheets 48 inches wide, and 54 inches wide in 1/2 and 5/8 inch board, in lengths from 8 to 14 feet. In metric mode the sheet list switches to 1200 mm widths, shown as about sizes.
What people use it for
Ordering board for a basement, garage or addition in one trip, comparing sheet sizes for the same walls, and checking a contractor's quote against your own count.
Common mistakes
- Buying exactly the area minus openings. Cut-outs are scrap. Keep a waste percent, or buy the larger count.
- Counting the ceiling at wall height. The ceiling is length × width.
- Forgetting the weight. Check the Chart tab before you carry 12-foot sheets.
- Measuring the outside of the wall. Measure the framing you are covering.
Questions
How many sheets of drywall do I need for a room?
Add the wall and ceiling area, subtract the openings, add waste and divide by one sheet's area. The page also lays real sheets out and tells you to buy the larger count.
How much waste should I allow?
The page starts at 10 percent as a placeholder you can change. Small rooms with many openings waste more.
How far apart do drywall screws go?
The IRC table lists a maximum of 12 inches on a ceiling, and 16 inches on a wall with 16 inch studs (12 inches with 24 inch studs). Type your own spacing, or leave it empty for the maximum.
How much joint compound do I need?
USG says about two 4.5 gallon pails of its ready-mix all-purpose compound per 1,000 square feet. The page scales that to your area.
Does the page know what drywall costs?
No. You type the price per sheet, pail, roll and box, and it multiplies. It says which lines it priced.
Can I use metric?
Yes. Press Metric to type meters and centimeters. Sheet sizes switch to 1200 mm widths. The page opens in your browser's system and remembers your choice.
Can I share my result?
Yes. Share makes a Facebook link with a picture, a link to copy and a TikTok video made on your device. The link keeps only the rooms, openings, sheet size and waste, for 90 days, never a price.
Related calculators
There is no map-tool job for drywall, which is interior work, so this page links the calculators hub.