How Much Plywood for a 12x16 Shed Floor?

How that number is worked out

These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.

Floor size compared

The common twelve foot wide floors, which is the widest a shed gets before it is a building. The middle column is the area divided by a sheet, before the waste allowance.

What else matters here

One hundred and ninety two square feet is exactly 6 sheets, with no remainder at all, and the calculator still says buy 7. That gap is the waste allowance and on a floor this size it is the right call, but it is worth understanding rather than accepting.

A floor that divides perfectly on paper still generates offcut in practice, because a sheet that is a quarter inch out of square, a joist that is a quarter inch off layout, or a wall that is not quite parallel all get absorbed by trimming. Six sheets with nothing spare means the first mistake costs a trip.

The bigger decision at this size is square edge against tongue and groove. Square edge sheets need blocking under every joint that does not fall on a joist, which on a 12 ft run means a line of blocking across the floor. Tongue and groove sheets carry the load across the joint themselves and need none, and they cost more per sheet than the blocking would. Seven sheets is where that stops being a rounding difference and starts being a decision.

What this calculator assumes

• A sheet is 4 by 8, which is 32 square feet, so three and an eighth sheets cover a square.
• Openings come off in full here, not at half. A window hole in a sheathed wall is a real hole and the offcut around it is what the waste line is for.
• The nail count is the fastener schedule rather than a rule of thumb: six inches around every edge and twelve inches into the framing in the field, so a sheet at 16 inch spacing takes 64 nails and one at 24 inch spacing takes 56. Eight penny common runs about 100 nails to the pound.
• Subfloor adhesive is figured on the linear feet of joist under the sheets, at about 84 feet of quarter inch bead from a 28 ounce tube, which is the size subfloor adhesive actually comes in.
• Roof sheathing wants H clips in each bay along the unsupported joint between rafters, which is four per sheet at 24 inches on center. At 16 inches most panel thicknesses do not need them, so the list leaves them off below 19.2 inch spacing.
• A subfloor gets screwed rather than nailed on most jobs, so the list carries the same fastener count in number eight screws at about ninety five to the pound and leaves the nail line under it as the alternative. Only one of those two lines gets bought.
• Thickness does not change the count, only the price and the span rating. Check the panel span rating against your framing spacing before you buy the thin one.

Questions people ask

Other common sizes