Plywood comes in one size and you cannot buy two thirds of a sheet. The area tells you almost nothing — what matters is how the sheets fall across the space, and how much of each offcut is too small to use anywhere else.
Floors, walls, roofs and sheathing. Enter the area and the sheet size, and get whole sheets.
Works in metric and US imperial — you choose at the start and can switch at any time. Every figure this calculator uses is published with its source, and the result comes with a printable order sheet. No account, no email, and nothing you type leaves your browser.
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Plywood comes in one size and you cannot buy two thirds of a sheet. What matters is how the sheets fall across the space and how much of each offcut is usable elsewhere. A 20 m² floor is 6.7 sheets by area at 2440 × 1220, which in practice is seven if the layout is kind and eight if it is not. Sketching the layout before ordering is the single most useful thing on this page.
The face grain runs along the length of the sheet and the sheet is stiffer in that direction, so on a floor or a roof the long dimension goes across the supports. That constrains the layout before any waste calculation starts. Joints should break bond like brickwork rather than lining up in a continuous seam, and on a floor every joint must land on a joist — which constrains it further.
Leave about 2 mm between sheets and 10 mm at the perimeter. Board butted tight will buckle when it takes up moisture, and it always takes up some. Check the actual thickness too: an 8 × 4 sheet is 2440 × 1220 mm, and 18 mm ply is usually 18 mm — but some imported board runs 17.5 where you expected 18, or 15 where you expected 16. Measure it rather than trusting the label, and order one spare on anything structural, because a damaged corner on the last sheet is a second trip for one board.
Divide the area by the sheet area — 2.98 m2 for a standard 2440 by 1220 sheet — then round up, and then sketch the layout, because where the joints fall usually adds a sheet. Area alone under-counts nearly every real job.
The face grain runs along the length of the sheet and the sheet is stiffer that way, so on a floor or roof the long dimension goes across the supports. It is a structural requirement, not a preference.
Yes — about 2 mm between sheets and 10 mm at the perimeter. Board butted tight will buckle when it takes up moisture, and it always takes up some.
Usually, but not always. Some imported board runs under the nominal size — 17.5 mm where you expected 18, or 15 where you expected 16. Measure a sheet rather than trusting the label, particularly where thickness is structural.