Plywood and Sheathing Calculator
Sheets of plywood or OSB for a floor, roof or wall from area and sheet size, with waste, rows and the offcut, and fasteners from your schedule.
Quick answer: sheathing sheets by area, 10 % waste
| Area | 4 × 8 | 4 × 9 | 4 × 10 |
|---|---|---|---|
| 200 ft² | 7 | 7 | 6 |
| 500 ft² | 18 | 16 | 14 |
| 1,000 ft² | 35 | 31 | 28 |
| 1,500 ft² | 52 | 46 | 42 |
| 2,000 ft² | 69 | 62 | 55 |
Sheets = area × 1.10 ÷ sheet area, rounded up. The calculator also works out the rows across the width and the strip cut off the last one, and multiplies the fastener count you enter from the schedule.
| Area | — |
|---|---|
| Sheets, bare | — |
| Sheets, with waste | — |
| Rows across the width | — |
| Fasteners | — |
Thirty-two square feet a sheet, and the plan decides the rest. Area over 32 is the floor of the count; the layout is the ceiling. Sheets run with their long edge across the joists and stagger by half a sheet each row, so the last row and the last sheet in every row are cuts, and a floor whose width is not a multiple of 4 feet wastes a strip per row. The 10% here covers that on a plain rectangle; a roof with hips and valleys wants 15.
Fasteners are a schedule, not a guess. How many nails or screws a sheet takes depends on the spacing the structural notes or the panel manufacturer call for, commonly closer along the edges than in the field, and on the support spacing under it. Count one sheet from your schedule and enter it; the page multiplies. It offers no default because a default would be a structural claim.
Tongue-and-groove and 4 × 9. T&G subfloor loses about half an inch of width to the tongue, so the sheets cover a little less than 32 square feet; the page ignores that, and the waste allowance absorbs it. Wall sheathing on 9-foot walls is sold in 4 × 9 to avoid the horizontal joint; choose it above and the rows follow.
Leave an eighth of an inch at every edge and end. APA, the Engineered Wood Association, recommends a 1/8-inch space between panel edge and end joints for its rated sheathing, floor panels and siding, because plywood and OSB expand with moisture and tightly butted panels have nowhere to go but up. Its builder tip (Form M300S) calls the gap a recommendation, not a requirement, notes that some manufacturers require it, and suggests a 10d box nail as the gauge. Tongue-and-groove joints get about 1/16 inch.
The gaps add up along a run; the sheet count does not change. Eight 4 ft sheets end to end with seven 1/8 in. gaps cover 32 ft 7/8 in., not 32 ft. Where the joints have to land on framing, that is the reason a long run ends in a trimmed sheet. The count on this page is in whole sheets and the waste allowance already pays for the trim.
Buckling is a matter of appearance, not of strength. APA says panel buckling may be an aesthetic or serviceability issue but is not a structural deficiency, that the gap need not survive once the panels acclimate, and that where the sheathing is flat enough the floor, siding or roofing can go on as planned. APA is a United States association; outside the United States the panel maker's instructions and the local code govern.
What I check on a job
Checking the rows against the framing plan. Before I trust the rows and the offcut line, I check which way the joists or rafters run. The page always counts rows across the shorter side, which assumes the framing spans that way. When it runs the long way, I count the rows across the length by hand, since the offcut strip moves with them; that also tells me how much of the waste allowance the last row will eat. Then the shape. A plan that is not one rectangle, an L or a floor with a stair opening, goes in as separate rectangles and I add the counts rather than forcing the whole plan into one length and width, since each piece gets its own rows and its own last-row offcut. Where the number runs short in practice is the stagger: 10% on a plain rectangle only works if the piece cut off the end of one row gets used to start the next. When those pieces get thrown out, even a plain rectangle comes up short.
Sheets = ceil(area × (1 + waste) ÷ sheet area). Rows = ceil(width ÷ 4 ft). Fasteners = sheets × fasteners per sheet, from the fastening schedule you enter. Sheet sizes are the nominal 4 × 8, 4 × 9 and 4 × 10.
Worked example
A 40 × 28 ft floor in 4 × 8 sheets: how many sheets?
- 1,120 ft² ÷ 32 = 35 sheets bare.
- With 10% for the staggered cuts: ceil(1,232 ÷ 32) = 39.
- Seven rows across 28 ft; at 60 fasteners a sheet from the schedule, 2,340 fasteners.
39 sheets. The fastener count is only as good as the schedule you enter — the page offers no default because spacing is a structural note, not a rule of thumb.
8 values on this page were driven in a browser and compared with independently derived figures on 2026-10-29 (2808 values across 228 calculators site-wide).
Questions
How many sheets of plywood for a 40 × 28 floor?
35 bare (1,120 ÷ 32) and 39 with 10% waste for the staggered cuts.
How many nails per sheet of sheathing?
It depends on the fastening schedule in the structural notes or the panel manufacturer's instructions — the spacing along edges and in the field, and the support spacing. Count one sheet from your schedule and the page multiplies; it does not assume a spacing.
Why do T&G subfloor sheets cover less than 32 sq ft?
The tongue takes about half an inch of the width. The page ignores that and lets the waste allowance absorb it; on 9 ft walls choose 4 × 9 sheathing to avoid a horizontal joint, and the rows follow.
What gap goes between sheathing panels?
APA recommends 1/8 in. at panel edge and end joints (Form M300S), a recommendation rather than a requirement; some manufacturers require it. A 10d box nail is the gauge, and the gaps do not change the sheet count.