Plywood Calculator
This plywood calculator tells you how many sheets to buy for a subfloor, wall, roof deck, or any other surface, working in square feet or square meters. Enter the area’s length and width (or a direct square footage), pick a 4×8, 4×10, or 5×5 sheet, set your waste allowance, and the sheet count rounds up for you.
Plywood sheets to buy
11sheets
- Area to cover320 sq ft
- Sheets before waste10 sheets
- Waste allowance (10%)+1 sheet
- Coverage bought352 sq ft
Formulas last reviewed on .
How the sheet count is calculated
Sheet goods are simple arithmetic with a round-up at the end:
Your area — length × width, or the direct square footage from the advanced field — is divided by one sheet’s coverage: 32 sq ft for the standard 4×8, 40 for a 4×10, 25 for a 5×5 Baltic birch panel. The waste factor scales that raw ratio up before the final round-up to whole sheets, and the results show the before-waste count and the waste sheets separately so you can see exactly what the allowance costs you.
The default 10% waste suits straightforward rectangular floors and walls where seams land on framing without drama. It’s an estimate you should adjust, not gospel: an open rectangle with few cuts can run 5%, while a chopped-up floor plan with closets, stair openings, and angles deserves 15%. Every offcut too small to span two joists or studs is waste whether you planned it or not — the allowance just admits it up front.
Worked example: sheeting a 20 × 16 ft garage attic floor
Say you’re laying a storage floor over the trusses in a 20-foot by 16-foot garage attic with standard 4×8 sheets and the default 10% waste. That’s what the calculator loads out of the box, so the numbers below match the result box above.
- Area: 20 × 16 = 320 sq ft to cover.
- Raw sheet count: 320 ÷ 32 = exactly 10 sheets — on paper, a perfect fit.
- Waste: 10 × 1.10 = 11, so the calculator says 11 sheets, one of them your waste line.
- Reality check: that “perfect” 10-sheet layout only works if the area is a true rectangle and every seam lands on a truss. It won’t be — the hatch opening, a plumbing vent, and staggered end joints all force cuts, and the eleventh sheet absorbs them.
Eleven sheets of 23/32″ ply is also about 660 lb going up a ladder, so recruit help. If your span between trusses is 24″, don’t be tempted to thin the sheet to save weight — sag is forever.
How many sheets of plywood do I need for 500 square feet?
The table below runs the formula for round areas from 100 to 1,000 sq ft with the default 10% waste, in both common sheet sizes. Find your square footage, or add two rows together for areas in between.
| Area (sq ft) | 4 × 8 sheets | 4 × 10 sheets |
|---|---|---|
| 100 | 4 | 3 |
| 200 | 7 | 6 |
| 300 | 11 | 9 |
| 400 | 14 | 11 |
| 500 | 18 | 14 |
| 600 | 21 | 17 |
| 700 | 25 | 20 |
| 800 | 28 | 22 |
| 900 | 31 | 25 |
| 1000 | 35 | 28 |
So 500 sq ft takes 18 standard sheets — not the 15.6 the bare division suggests. The 4×10 column earns its keep on tall walls and wide floors: fewer sheets means fewer seams to block, but check that you can actually transport and handle a 10-foot panel before ordering.
Frequently asked questions
What thickness of plywood do I need for subfloor versus sheathing?
Subfloors carry live loads, so they’re the heaviest: 23/32″ (sold as 3/4″) tongue-and-groove is the standard over joists at 16″ or 19.2″ on center. Wall sheathing does far less work — 7/16″ or 1/2″ is typical. Roof decks fall in between at 1/2″ to 5/8″ depending on rafter spacing and snow load. Thickness doesn’t change the sheet count in this calculator, but it triples the weight you’ll be hauling, so decide before ordering.
Can I use OSB instead of plywood?
For structural sheathing and subfloors, yes — OSB carries the same span ratings at a noticeably lower price, which is why most new construction uses it. Plywood still wins where moisture is a factor: it dries out faster and its edges don’t swell the way OSB’s do, so roof decks in wet climates and bathroom floors are worth the upgrade. The math on this page is identical either way; both come in 4×8 sheets.
How should I stagger plywood seams, and does it change the count?
Run sheets with the long edge perpendicular to the joists or studs, and offset each row’s end joints by half a sheet — like brickwork — so four corners never meet at one point. Staggering is exactly why the waste allowance exists: each offset row starts with a cut sheet, and the offcut only gets reused if it still spans two supports. A straight-grid layout would waste less paper but makes a weaker, squeakier floor.
What can I do with leftover plywood offcuts?
Keep anything bigger than about a square foot. Half sheets become shelving, garage cabinets, or drawer bottoms; strips rip into blocking between joists, gussets, and jigs for your saw; even small squares make shims and clamping pads that save good faces from dents. A 10% allowance on a 320 sq ft job leaves roughly one sheet’s worth of offcuts — that’s a workbench top, not trash.
Why do cabinetmakers use 5×5 Baltic birch sheets?
Baltic birch is made with more, thinner plies and a void-free core, so edges machine cleanly and screws bite anywhere — ideal for drawer boxes and jigs. The 5×5 ft format is simply the mill standard it’s produced in. In this calculator, pick the 5×5 option (25 sq ft per sheet) and expect counts about 28% higher than 4×8 coverage; for casework, estimate from your cut list instead of floor area, since parts nest tighter than full-sheet math implies.
These results are planning estimates only — verify quantities with your supplier and local building code before you buy or build. See our terms of use.