Plywood sheet calculator
How many sheets of plywood a set of panels needs. Give each panel’s overall length and widest point; anything longer than a sheet is scarfed from pieces, and the joints are allowed for.
Result
4 panels, 89 sq ft (8.3 m²) with margins. Each scarf overlaps 2 in. The layout uses 56% of the plywood bought. Buy one more than this if you can: a sheet spoiled halfway through costs more in waiting than in money.
How this is worked out
Each panel is treated as the rectangle around it, its overall length by its widest point, plus the margin all round for the saw cut and truing up. Long side along the sheet.
Scarf joints. A panel longer than the sheet is made from pieces glued end to end with a scarf. The two bevels overlap by the scarf ratio times the thickness, so an 8 to 1 scarf in 6 mm ply overlaps 48 mm (2 inches in 1/4 inch ply). The first piece is a full sheet length and each further piece adds a sheet length less that overlap.
Laying out. The pieces are sorted widest first and laid along each sheet in rows, starting a new row when the length runs out and a new sheet when the width does. That is the simple layout a person would draw on the sheets and is the figure to buy against. The area figure beside it is the floor: what you would need if panels tiled the sheets with no gaps at all. Curved panels nested head to tail can land somewhere between the two.
A designer’s own nesting plan beats both. If your plans come with one, use it and use this to check it.
Plywood boats people are logging here
Stitch-and-glue and plywood designs with public build logs, including how many hours each step took.
- Northeaster Dory · 3 logs
- Caladesi Carolina Dory · 2 logs
- Squirt · 2 logs
- 14 ft Rapid Robert · 1 log
- Cabin Skiff · 1 log
- Cape Cutter 19 · 1 log
Questions people ask
How many sheets of plywood does a small boat take?
A canoe or a small stitch-and-glue skiff often takes three to five sheets, a 16 foot skiff six to ten, and a larger daysailer more. The designer's material list is the real answer; this calculator is for checking it, or for a design that does not have one.
What scarf ratio should I use for plywood?
An 8 to 1 scarf is the usual standard for marine plywood, so a 6 mm (1/4 inch) sheet needs a bevel about 48 mm (2 inches) long. Some builders and designers use 10 or 12 to 1 for heavily loaded joints. Each joint uses up that much length from the two pieces it joins.
Are 4x8 sheets the same as 1220 x 2440 mm?
Nearly. A 4 by 8 foot sheet is 1219 by 2438 mm, a couple of millimeters smaller each way than a metric 1220 by 2440 sheet. Many marine plywoods are sold at 1220 by 2440 even in the United States, and some European makers sell 1250 by 2500.
Why is the sheet count higher than the area suggests?
Panels are not rectangles that tile a sheet perfectly. The area figure is the floor nobody can beat; the sheet count lays panels out in simple rows the way a person would, with a margin for the saw. Nesting curved panels head to tail can get closer to the area figure.