Plywood and OSB Sheet Calculator
Enter the area you are sheathing and the panel size you are buying. This calculator returns the number of sheets, the coverage you actually get once the panels are spaced the 1/8 in APA recommends, and the cost. Panel spacing is not a detail: tightly butted panels have nowhere to expand, and they buckle.
Sheets to order
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Results are estimates for planning purposes. Verify with your supplier, engineer, or a qualified professional before ordering material or performing work.
Panel coverage, before and after spacing
| Panel | Nominal area | Spaced 1/8 in | Panels per 1,000 ft² |
|---|---|---|---|
| 4 × 8 ft | 32.00 ft² | 32.13 ft² | 32 |
| 4 × 9 ft | 36.00 ft² | 36.14 ft² | 28 |
| 4 × 10 ft | 40.00 ft² | 40.15 ft² | 25 |
| 4 × 12 ft | 48.00 ft² | 48.17 ft² | 21 |
| 54 in × 9 ft | 40.50 ft² | 40.64 ft² | 25 |
Spaced coverage is (panel width + 1/8 in) × (panel length + 1/8 in). Panels per 1,000 ft² use the spaced figure, rounded up, with no waste added. PS 2-18 allows ±1/16 in on the manufacturer's stated panel size, so a stack of panels is never exactly 96 in — one more reason the gap matters.
What decides the panel, and what does not
- Buy by span rating and Performance Category, not by thickness. PS 2-18 defines the Performance Category (7/16, 15/32, 19/32 and so on) as a designation tied to a thickness range, with a ±1/32 in tolerance up to 13/16 in. The number on the stamp is a category, not a caliper reading.
- Gap the panels. APA's Builder Tip M300 is one sentence long in practice: always space wood panel sheathing 1/8 in. A 10d box nail is the gauge. Panel edge clips do the same job on roof sheathing.
- This tool counts area, not layout. A run of wall that finishes 2 in past a panel edge still costs a full sheet, and the offcut may or may not be usable elsewhere. On cut-up roofs, lay the panels out on paper before you trust any area-based count.
- Orientation, nailing and blocking are structural. They come from your drawings and the panel's span rating. The sheet count does not change with them; the performance of the wall very much does.
- Subfloor is usually tongue-and-groove. T&G panels lose a little coverage to the joint, and APA's spacing guidance applies to the ends, not across the machined edge. Check the panel's own installation instructions.
How it's calculated
- Net area
A (ft²) = length × width − openings- Coverage of one panel, spacing included
coverage (ft²) = (panel width (in) + gap) × (panel length (in) + gap) / 144A 4 x 8 panel is 48 by 96 in with a tolerance of ±1/16 in on the manufacturer's stated size (PS 2-18 section 5.2.1.1). Spaced 1/8 in on both edges, each panel occupies 48.125 by 96.125 in, or 32.13 ft² — slightly more wall per sheet than the nominal 32 ft².- Sheets to order
sheets = ceiling( A × (1 + waste %) / coverage )- Cost
cost = sheets × price per sheet
Frequently asked questions
Thirty-two sheets of 4 x 8 covers 1,024 ft² with no waste and no gaps. Spaced 1/8 in as APA recommends, each panel occupies 32.13 ft², so 32 sheets cover 1,028 ft². Add your own allowance for cuts: 10% takes the order to 35 sheets.
32 square feet. With the 1/8 in spacing APA recommends at edges and ends, each panel occupies 48.125 by 96.125 in on the frame, which is 32.13 ft².
APA recommends 1/8 in at all panel edges and ends and is explicit about why: panels take on and give up moisture, and a tightly butted panel has nowhere to go but up. APA calls it a recommendation rather than a requirement, and suggests a 10d box nail as the field gauge. Some panels are manufactured slightly undersized so that gapping happens automatically.
Not exactly, and the standard says so. PS 2-18 calls 7/16 a Performance Category — a designation tied to a thickness range, with a manufacturing tolerance of ±1/32 in on panels 13/16 in and under. Buy by Performance Category and span rating, not by a caliper reading.
That is a structural question, not a quantity one. Orientation affects the span rating you can use, the nailing pattern and the shear value of the wall, so it comes from your drawings, the panel's span rating and your building department — the sheet count is the same either way.
It depends entirely on the shape of what you are covering. A plain rectangular wall or a simple gable can come in near zero; a cut-up roof with hips, valleys and dormers can run well past 15%. No standards body publishes a waste factor, which is why this calculator asks you for yours instead of inventing one.
Sources & references
- NIST Voluntary Product Standard PS 2-18, Performance Standard for Wood Structural Panels — section 5.2.1.1 size tolerance (±1/16 in on stated length and width), section 2.10 Performance Category, section 5.2.1.2 thickness tolerance — The NIST voluntary product standard that plywood and OSB structural panels are manufactured and trademarked to.
- APA — The Engineered Wood Association, Builder Tip M300: Prevent Buckling with Proper Spacing — always space wood panel sheathing 1/8 in at edges and ends — APA states this is a recommendation to minimize buckling, not a code requirement. A 10d box nail is the field gauge for 1/8 in.
- NIST Voluntary Product Standard PS 1-19, Structural Plywood — The companion standard for all-veneer structural plywood; PS 2 covers OSB and other mat-formed and composite panels.
Content checked against these sources — last reviewed September 19, 2026.