Subfloor Sheet Calculator
Count the 4×8 subfloor sheets of plywood or OSB for a floor, with waste, plus the adhesive and screws to fasten them.
How it works
sheets = ceil(area ÷ 32 × (1 + waste)) · adhesive tubes = area ÷ 50 · screws ≈ 40 per sheet
A 4×8 sheet covers 32 sq ft, so the floor area divided by 32 is the bare sheet count; the waste allowance covers cuts at walls and staggered end joints. Subfloor is glued and screwed to the joists — figure a tube of construction adhesive per 50 sq ft and about 40 screws per sheet (6 in on the edges, 12 in in the field) to stop squeaks.
Worked example
A 20 × 16 ft floor is 320 sq ft ÷ 32 = 10 bare sheets. With 10% waste that rounds to 11 sheets, needing about 7 tubes of adhesive and 440 screws — five boxes of 100.
Frequently asked questions
Plywood or OSB for subfloor?
Both are code-approved and rated by span. OSB is cheaper and dominant in new construction; plywood handles occasional moisture a little better and dries flatter. Match the panel thickness to your joist spacing — 3/4 in tongue-and-groove is standard at 16 in on-center.
Why glue as well as screw?
Glue bonds the panel to the joist so the floor moves as one, which is the single biggest thing you can do to prevent squeaks. Screws hold it tight while the adhesive cures and resist withdrawal far better than nails.
How much waste should I add?
Ten percent is fine for a plain rectangular room. Add more — 15% or so — for lots of angles, bump-outs or a stairwell opening, where offcuts pile up and full sheets get chopped down.
Related calculators
Estimates only — add for waste and confirm every load-bearing decision against local building codes and a design professional.