Sheet sizes and real thicknesses
Inch Calculator’s table of plywood sizes gives 4 × 8 ft as the size plywood is most often sold in, which is 32 sq ft, and adds that hardwood plywood often comes in 5 × 5 ft as well: 25 sq ft. Choose either in the options, or type the size of the sheet you have.
A sheet is thinner than its name. The same table puts a 3/4 in sheet at 23/32 in and a 1/2 in sheet at 15/32 in, and says a caliper is the only sure measure. Thickness changes no count here, but it changes every joint you cut to fit: measure the sheets you bought before you set a dado.
Area mode and waste
For a subfloor, a wall or a roof deck, enter each surface. The calculator adds them up, then turns the total into whole sheets.
Worked example. A subfloor 12 ft by 16 ft, in sheets of 4 × 8 ft.
- Area: 16 ft × 12 ft = 192 sq ft
- Sheets: 192 ÷ 32 = 6 exactly, so 6 sheets with no extra
- With 10% for the cuts: 6.6, so 7 sheets
The extra is there because a sheet rarely lands on the last joist or stud, and the piece cut off is not always long enough to start the next row. 10% is where the calculator starts; it is yours to change, down to nothing for a room that divides evenly.
A roof is covered along its slope, which is longer than its plan. Add a roof with its pitch and the calculator multiplies for you: a roof plane 30 ft long and 14 ft wide on the plan is 420 sq ft flat, 469.57 sq ft at a pitch of 6 in 12, and takes 17 sheets with the extra.
Cut layout
Switch to "Cutting layout" for a list of parts. Give each line a width, a length and how many, and the calculator lays them out on as few sheets as it finds, draws each sheet with a letter on every part, and writes the cuts in order.
How it works: the widest part goes first. Each sheet is ripped along its length into strips, and each strip is then cut across into its parts. That is the order a table saw or a track saw wants, with the long cuts made while the sheet is still whole.
- Kerf. Every cut turns a blade’s width into sawdust. The calculator starts at 1/8 in (0.125 in), a full-kerf blade: measure yours. Eight parts of 11 3/4 × 47 1/2 in fit on one 4 × 8 sheet, 47.375 in across and 95.125 in along with the cuts. A ninth takes a second sheet.
- Grain. A part is turned on the sheet where that is the only way it fits. Lock the grain of a part and it stays the long way of the sheet, as a door or a drawer front should.
- Edge trim. If you cut the factory edges off before you start, enter how much: the layout stays inside what is left.
The layout is a good one, not a proved best. Read the diagram against your list before the first cut, and the yield under it: the share of the plywood that ends up in parts.
Plywood, OSB or MDF?
The count is the same for any panel of the same size, so the area mode serves for OSB sheathing as it does for plywood. Which one a floor or a roof may be built with is for your code and your plans to say, not for a calculator.
MDF is a different sheet in one way that matters to a layout: the same source notes that a full sheet is typically an inch over, 49 × 97 in. Enter it as "Other size" and the parts are laid out on the real sheet.
Questions about plywood
How many sheets of plywood for a 12×16 floor?
6 sheets of 4 × 8 ft cover it exactly: 192 sq ft. With 10% for the cuts, buy 7.
How much does a sheet cover?
A 4 × 8 ft sheet covers 32 sq ft, and a 5 × 5 ft sheet 25 sq ft.
What is kerf?
The width of the cut a saw blade makes. Every cut removes that much, so parts that add up to the width of a sheet do not fit on it. The calculator starts at 1/8 in.
Can the parts be turned on the sheet?
Yes, where turning is the only way a part fits. Set a part’s grain to "Lengthwise" to keep it from turning: it then stays the long way of the sheet.
Sources
- Inch Calculator, Actual Plywood Thickness and Size. Plywood is most often sold in 4 x 8 ft sheets, and hardwood plywood often in 5 x 5 ft as well. The actual thickness is often 1/32 in under the nominal: a 3/4 in sheet is 23/32 in, a 1/2 in sheet 15/32 in. A caliper is the only sure measure. MDF is sold in 4 x 8 ft sheets too, and a full sheet is typically an inch over each way: 49 x 97 in. Read on .
Updated . How we calculate. Found a mistake? Tell us.