Plywood cut calculator: how many pieces from a sheet, and how to lay them out

How the calculator lays out a sheet

Every cut it plans goes straight through, from one edge of the piece in your hands to the other. That is the only kind of cut a table saw, a panel saw or a track saw on a rail can make, so any layout it draws is one you can actually cut. The list under each sheet gives those cuts in an order that works: each one is across a piece the earlier cuts have already freed.

It puts the largest parts down first, each on the first sheet that still has room for it. Then it tries a few different orders and first-cut directions — ripping strips first, crosscutting panels first — and keeps the plan that uses the fewest sheets. That is the whole method. It does not search every possible arrangement, so on some jobs a person with a pencil will find a layout that saves a cut or leaves a tidier offcut.

The kerf is taken out wherever a cut is made and nowhere else, so a part can sit flush against the factory edge. With “parts may be turned” ticked, a part can be rotated through 90° to make it fit. Unticked, every part keeps its length along the length of the sheet.

The example is a bookcase 72 in tall in 3/4 in plywood: two sides and five shelves, 11 1/4 in deep. Change any number and the layout is worked out again as you type.

Reading the cut list at the saw

Under each sheet is a numbered list of cuts. A rip runs the long way of the sheet — along the grain, on most plywood — and acrosscut runs across it, whatever shape the piece in your hands has become by then. The measurement is taken from the end for a crosscut and from the edge for a rip, on the same side the drawing puts at its left and top — so the first cut on a fresh sheet is measured from its factory edge.

Each line also names the two pieces the cut leaves behind, so you can check your tape against the list before the blade goes in: if the offcut in your hand is not the size the list says, something moved, and it is cheaper to find out now than three cuts later. When a cut says “the rest is kerf”, the blade is trimming a sliver no wider than itself and nothing is left on that side.

Pencil a number on every part as it comes off. Sheets of similar pieces look alike on a cart, and a shelf that is 1/4 in short looks exactly like one that is right until it is in the carcass.

Working it out by hand

For pieces of a single size the arithmetic is short. Along one edge of the sheet, the number of pieces that fit is

pieces = (sheet + kerf) ÷ (piece + kerf), rounded down

The extra kerf on the top line is there because four pieces need only three cuts between them, not four.

Take 12 × 24 in pieces from a 48 × 96 in sheet with a 1/8 in blade. Across the 48 in width, 48 1/8 ÷ 12 1/8 = 3.97, so three pieces rather than four. Along the 96 in length, 96 1/8 ÷ 24 1/8 = 3.98: three again. A straight grid gives 3 × 3 = 9.

Then look at what is left. Three 12 in widths and the two kerfs between them use 36 1/4″ of the sheet, and one more kerf leaves a strip11 5/8″ wide — too narrow for anything on this list. Three 24 in lengths use 72 1/4″, leaving 23 5/8″ across the end of the grid. A 12 × 24 in piece turned sideways fits in that, and that is the tenth. The calculator above finds the same 10.

Mixed sizes are where the hand method runs out of patience. Each part you place changes the shape of what is left for the next one, which is exactly the tedious part a calculator is for.

Why the blade eats more of the sheet than you expect

A kerf of 1/8 in sounds like nothing, and on a single cut it is. It turns into a whole lost row when pieces are sized to divide the sheet evenly, because then there is no slack at all: 12 in goes into 48 in exactly four times, and the three cuts between those pieces need 3/8 in that the sheet does not have.

Here is how often that happens with sizes people ask about. Every column assumes a 48 × 96 in sheet, a 1/8 in kerf, no edge trim and pieces that may be turned, and every number is worked out by the same code as the calculator.

The 24 × 24 in row is the one that surprises people. Two pieces across the width need 48 1/8 in, so only one fits, and four along the length need 96 3/8 in, so only three do. Arithmetic says eight; a real blade at full size gets three.

Cut them a hair small, when you can

The last column is the practical answer. If a shelf, a drawer bottom or a shop jig does not care about the final eighth of an inch, size it down and the lost row comes back:16 pieces of 11 7/8″ × 23 7/8″ come out of the same sheet that only gave 10 at exactly 12 × 24.

The parts that cannot give anything up — cabinet sides that meet a face frame, panels that sit in a groove, doors with a set reveal — are the ones to size first. Plan them at their true size, let the forgiving parts absorb the kerf, and run the calculator again to see what that buys.

Grain direction

On most sheets the face veneer runs along the length. Anything that will be seen — a cabinet side, a door, a shelf with its edge on show — usually wants the grain running the long way of the part, so the part’s length has to follow the sheet’s.

Untick “parts may be turned” and the calculator keeps every part that way round. On the example bookcase that is the difference betweenone sheet andtwo sheets. With turning allowed,two of the shelves lie across the end of the sheet beside the sides — which also means their grain runs across them. Whether that saved sheet is worth it depends on whether anyone will see those shelves.

There is one switch for the whole job. If some parts care about grain and others do not, work out the grain-matched parts first, then the rest on what is left.

Sheet sizes you will actually buy

• North America: 4 × 8 ft, which is 48 × 96 in.
• UK and much of Europe: 2440 × 1220 mm, about96 1/16″ × 48 1/32″ — close enough to the imperial sheet that it is easy to plan on the wrong one.
• Parts of mainland Europe: 2500 × 1250 mm is common, particularly for OSB and construction plywood.
• Baltic birch: usually 1525 × 1525 mm, sold as 5 × 5 ft.

Measure before you trust the label. Some panels arrive slightly oversize, and factory edges are not always clean enough to use as a finished edge — if you plan to trim them, choose “Custom size” and enter the sheet a little smaller.

Thickness has the same gap between the name and the fact. Plywood sold as 3/4 in often measures 23/32 in, and 18 mm is the usual metric equivalent. The layout does not depend on thickness, but your joinery does.

Before the first cut

A layout is only as good as the numbers typed into it. Three checks take five minutes and save the sheet:

1. Measure your kerf. Cut a scrap, measure the piece and the offcut, and subtract both from the original. Enter that, not the number on the blade’s packaging.
2. Measure the sheet. Check both edges and both ends, and check that the corners are square. If a factory edge is chipped or out of true, plan on trimming it and enter the sheet that small.
3. Size the exact parts first. Work out which dimensions have to be right to the sixty-fourth and which can give, before you type anything. Change the forgiving ones, never the exact ones, to make a layout fit.

Then break the sheet down into pieces you can handle before chasing precision. A full sheet of 3/4 in plywood is heavy and awkward against a fence, and a clean second cut on a manageable piece beats an accurate first cut you had to wrestle.

Waste, or stock for the next job?

A waste percentage is a blunt number. Two plans can waste exactly the same area and be worth very different amounts: one leaves a dozen thin strips, the other a single rectangle big enough for the next project. That is why the result names the largest offcut on the last sheet, and why the percentage counts that offcut as waste rather than pretending it away.

There is more on getting usable leftovers — and on the order of cuts that keeps a heavy sheet manageable — inhow to cut a sheet of plywood with the least waste. Building a bookshelf, kitchen cabinet or workbench? Thecut list templates work the parts out from the outside measurements first. Pricing solid timber rather than sheets? Theboard foot calculator works out volume and cost.

Questions

How many pieces can I cut from a 4 × 8 sheet of plywood?

It depends on the size of the pieces and on your blade. For 12 × 24 in pieces from a 48 × 96 in sheet, the arithmetic says 16. With a 1/8 in kerf and the pieces cut to exactly 12 × 24 in, 10 fit. Cut them to 11 7/8″ × 23 7/8″ and all 16 fit again. The table on this page has other common sizes, and the calculator works out any mix of parts.

How much does a saw blade take out of a sheet?

The width of its cut, called the kerf. Full-kerf table saw blades cut about 1/8 in and thin-kerf blades about 3/32 in, but the number that matters is your own saw’s: cut a test piece, measure the parent board and the offcut, and subtract. Every cut costs one kerf, so a plan with ten cuts loses ten of them.

Should I let the calculator turn parts?

Yes, for anything painted or hidden — a cabinet back, a drawer bottom, a jig — because the extra freedom often saves material. No, for parts whose grain has to run along their length, such as visible cabinet sides and doors: untick the box and every part keeps its length along the length of the sheet.

Why does my job need more sheets than the area suggests?

Dividing the total area of your parts by the area of a sheet ignores three things. Every cut removes a kerf. Rectangles of different sizes almost never tile a sheet without gaps. And a part cannot be tucked into a notch, because every cut has to run straight across the piece being cut.

What does the waste percentage count?

Everything that does not end up in a part: the material turned to dust by each kerf and every offcut, including the usable piece left on the last sheet. That makes the figure honest but blunt, so the result also names the largest offcut, which is often worth keeping.

What size is a sheet of plywood?

In North America, 4 × 8 ft, which is 48 × 96 in. In the UK and much of Europe, 2440 × 1220 mm. Some panels are sold a little oversize and factory edges are not always usable as finished edges, so measure the sheet you buy and enter it slightly smaller if you plan to trim it.

Do I have to sign up, and is anything I enter saved?

No sign-up. The layout is worked out in your browser: once the page has loaded it needs no connection, nothing you type is sent anywhere, and nothing is kept after you close the tab.