Panel count, thickness, adhesive and screw schedule for a new subfloor.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
| Lumber & Decking | $271–$367 |
| Fasteners & Hardware | $120–$162 |
| Total | $391–$529 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Enter the size of the floor and the joist spacing it's built on, and the Subfloor Calculator sizes the structural panels — OSB or CDX plywood, in the correct thickness for that span — along with the adhesive and screw schedule to fasten them down tight and squeak-free.
It accounts for staggered panel rows, a trim waste allowance, and whether you're using tongue-and-groove or square-edge panels, since square-edge joints that fall between joists need their own blocking. The result is a materials list you can hand straight to the lumberyard.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Check joist spacing, level and condition before ordering panels — this calculator's thickness recommendation only holds if the joists underneath are sound and at a standard spacing.
Dry-lay the sheet layout on paper so end joints stagger at least one joist bay between rows, and mark where trim cuts fall around the room's perimeter and any openings.
Before setting each sheet, snap chalk lines across its top face at the joist spacing so screws land on solid framing once the panel is down and the joists are hidden.
Apply a serpentine bead of subfloor adhesive along every joist the panel will cross, working one panel at a time so the glue doesn't skin over before the panel is set.
Lay the panel with a 1/8" gap at edges and ends, tapping tongue-and-groove joints tight with a block and hammer or pry bar before fastening.
Drive screws at 6" on-center along all edges and 12" on-center through the field into each joist, following your chalk lines so nothing is fastened to air.
If you're using square-edge panels, install 2× blocking under any joint that doesn't fall on a joist before moving to the next row.
Walk the finished subfloor and drive an extra screw anywhere you hear movement or feel a soft spot before the finish flooring goes down.
Equip the job
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Keep planning
Interior & Finishing
Answers
Thickness is set by how far the panel has to span between joists, not by preference. At 12" on-center joist spacing, 1/2" (15/32" APA-rated) panels are typically enough; at 16" spacing, step up to 5/8" (19/32"); at 24" spacing you need 3/4" (23/32") tongue-and-groove panels rated for that span. Always check the panel's own APA span-rating stamp against your actual joist spacing — it overrides any rule of thumb.
Both are code-approved and perform similarly once installed correctly. OSB is cheaper and comes with more consistent thickness sheet to sheet; plywood dries out faster if it gets wet during construction and holds screws marginally better at the edges. Either works fine under tile, hardwood, vinyl or carpet — the bigger factor is getting the thickness and fastening schedule right, not the species.
Screws alone will hold the floor down, but adhesive is what keeps it quiet. A bead of subfloor adhesive on every joist before the panel goes down bonds the panel to the framing across its whole length, not just at the screw points, which is what stops the small movements that cause squeaks over time. It's inexpensive relative to the labor of a floor, so glue-and-screw is worth doing on every job.
A standard pattern is screws at 6" on-center along all panel edges and 12" on-center through the field of the panel into each joist it crosses. Stagger the end joints between rows so four panel corners never meet at one point, and leave a 1/8" gap at every edge and end for the panel to expand and contract with humidity.
Yes. Tongue-and-groove panels interlock along their long edges, so that joint is self-supporting between joists. Square-edge panels have no such interlock — any joint that doesn't land directly on a joist needs solid 2× blocking underneath it, or that edge will flex and eventually squeak or crack the finish flooring above it.
Sometimes, if the existing floor is flat, sound and well-fastened — a thin layer can be added as underlayment rather than structural subfloor. But if the existing panels are damaged, spongy, or squeaking, that's a sign the structural layer has failed and needs full replacement, not a layer on top of the problem. When in doubt, pull a section up and check the joists and old panel condition first.