Plywood & Sheet Goods Calculator
Enter the area and the sheet size and this gives you the sheet count. It works for plywood, OSB, MDF, cement board or anything else sold by the sheet.
Sheets needed
17sheets
- Area
- 480.0 sq ft
- With waste
- 528.0 sq ft
- Sheet covers
- 32.0 sq ft
- Square metres
- 49.05
- Includes a 10% waste allowance. The bare figure is 480.00 sq ft.
- This is an area divided by an area, so it assumes the offcuts get used. On a floor or a roof they mostly do. On a job where every sheet has to run a particular way, count the sheets across and down separately and take the larger answer.
- Sheets are laid with the joints staggered and, on a floor or roof, running across the joists rather than along them.
About the sheet goods calculator
Sheet materials are the simplest thing in this category to count and the easiest to get slightly wrong. The arithmetic is an area divided by a sheet area — a 4 by 8 sheet covers 32 square feet, so 480 square feet of subfloor takes fifteen sheets. What that assumes is that the offcuts get used somewhere.
On a floor or a roof they mostly do, because the sheets are laid in courses with the joints staggered and the piece cut off the end of one row starts the next. On a job where every sheet has to run a particular way — cabinet backs, a feature wall, anything where the grain direction shows — they often do not, and the honest count is sheets across multiplied by sheets down, each rounded up separately.
Sheet sizes are not all 4 by 8. Nine and ten-foot sheets are sold for walls with tall ceilings, hardwood ply often comes 4 by 4 or 5 by 5, and metric sheets are 1200 by 2400 millimetres, which is slightly narrower and shorter than a 4 by 8. Enter what you are buying.
What it works out
- Sheet counts in any sheet size, imperial or metric
- Area in square feet and square metres
- A waste allowance for cuts
- Plywood, OSB, MDF, cement board and drywall panels
The formula
Sheets = (Area × (1 + Waste)) ÷ (Sheet length × Sheet width)
An area divided by an area. A 4 by 8 sheet covers 32 square feet, so 480 square feet of floor is fifteen sheets before waste and seventeen with ten per cent on top.
The assumption underneath it is that the offcuts get used. Laying a floor or sheathing a roof, they do: the sheets run in courses with the joints staggered, and the piece cut off the end of one course starts the next. That stagger is not cosmetic — a joint running the full width of a floor is a weak line, and staggering them is what stops it.
Where the assumption breaks is any job where the sheets have to run a particular way and the offcuts cannot be turned round. There, count how many sheets go across and how many go down, round each up on its own, and multiply. It is a larger number, and it is the right one.
On a floor or roof the sheets also run across the joists rather than along them, so the sheet spans several supports rather than sitting between two.
- Area
- The surface being covered — length times width.
- Sheet length
- The long side of the sheet, usually 8 feet or 2400 mm.
- Sheet width
- The short side, usually 4 feet or 1200 mm.
- Waste
- Extra for cuts. Ten per cent on a plain rectangle, more with obstructions.
A worked example
A twenty-four by twenty foot subfloor in 4 by 8 sheets, with ten per cent for cuts.
That works out to 17 sheets.
- Area
- 480.0 sq ft
- With waste
- 528.0 sq ft
- Sheet covers
- 32.0 sq ft
- Square metres
- 49.05
Questions
How many sheets of plywood do I need for 500 square feet?
Sixteen 4 by 8 sheets, since each covers 32 square feet. With a ten per cent waste allowance you would buy eighteen.
How many square feet is a sheet of plywood?
32 for a standard 4 by 8 sheet. A 4 by 9 covers 36 and a 4 by 10 covers 40. A metric 1200 by 2400 mm sheet covers 31 square feet, very slightly less than a 4 by 8.
Should I use plywood or OSB for a subfloor?
Both are rated for it and OSB is cheaper. The practical difference is water: OSB swells at cut edges if it gets wet and does not fully recover, while plywood dries out closer to flat. If the deck is going to sit exposed for a while before the roof goes on, that matters.
How thick should subfloor plywood be?
It depends on the joist spacing, and the sheet is stamped with what it is rated for. As a guide, 5/8 inch suits joists at 16 inch centres and 3/4 inch is usual at 19.2 or 24. Tile and stone floors want more than the minimum because they crack on any deflection.
Which way should the sheets run?
Across the joists or rafters rather than along them, so each sheet spans several supports instead of sitting between two. Stagger the end joints between courses as well — a joint running the full width of a floor is a weak line.
Does this count the offcuts as usable?
Yes. It divides one area by another, which assumes the piece cut off the end of a course starts the next one. That is how a floor or roof goes down. If your sheets all have to run one way and cannot be turned, count the sheets across and down separately and multiply — you will need more.
How much waste should I allow?
Ten per cent on a plain rectangle. Fifteen to twenty if the area has stairwells, chimneys or bays to cut round, because each obstruction turns a full sheet into two awkward pieces.
How much does a sheet of plywood weigh?
A 3/4 inch 4 by 8 sheet of softwood plywood is around 60 to 70 pounds, and OSB of the same size is a little heavier. It is a two-person lift up a ladder, and a pallet of them needs somewhere flat and dry to sit.