Plywood Cut List Optimizer

How the optimizer works — honestly

This tool runs a guillotine packing heuristic: parts are sorted several ways (largest area first, longest side first, widest first, …), each ordering is packed with edge-to-edge cuts, and the best result — fewest sheets, then least waste — wins. That makes it fast and deterministic, and every layout it draws is valid: parts never overlap, never hang off the sheet, and every placement accounts for the blade kerf on its right and bottom edges. What it is not is a guaranteed mathematical optimum. True optimal 2D cutting is a famously hard problem; a good heuristic gets within a sheet of optimal on realistic lists, and its guillotine layouts have a practical advantage — every cut runs edge to edge, so you can actually make them on a table saw or track saw.

Why grain direction locks matter

Plywood has a face veneer with visible grain running the sheet’s long dimension. Rotating a part 90° on the sheet turns that grain sideways — invisible inside a carcass, glaring on a door panel or drawer front. The grain lock checkbox tells the optimizer a part’s grain must run along its length, so it will never rotate that part, even when rotating would save material. Lock show surfaces; leave hidden parts free and let the optimizer earn its keep.

Worked example

The default parts list is a small base cabinet: two sides at 24″ × 30″ (grain locked), four shelves at 22 3/4″ × 23 1/4″, and a top and bottom at 24″ × 23 1/4″. On 4×8 sheets with a 1/8″ kerf the optimizer packs all eight parts onto two sheets — the first at about 78% utilization (both locked sides, the top and bottom rotated alongside them, and two shelves), the second holding the last two shelves at 23%. Total part area is 4,670 in² against 4,608 in² per sheet, so one sheet was never possible: the area alone overflows it before a single kerf is counted. That check — part area vs. sheet area — is worth doing by hand on any quote, and the optimizer’s layout tells you the rest: how the parts actually land, and whether the offcut on sheet two is big enough to keep.

Reading the diagram at the saw

Because every layout here is a guillotine layout, each cut runs edge to edge — the diagram is not just a picture of where parts sit, it is a cutting sequence. Work it in this order: make the full-length rips first, splitting the sheet into strips while it is still one stiff, easy-to-reference panel, then crosscut each strip into its parts. Rips walk the fence once per strip; crosscuts then handle pieces small enough to control. This is exactly the track-saw workflow too: drop the sheet on foam, run the long guided cuts through the whole panel, and break the strips down at the mitre saw or table saw — no cut in the diagram ever requires a stopped (partial) cut, a jigsaw notch, or a plunge in the middle of a panel.

Two shop habits make the diagram trustworthy. First, cut on the correct side of the line: the optimizer already charges the 0.125″ default kerf (or whatever you entered) to the right and bottom of each part, so the drawn part sizes are the finished sizes — put the blade in the waste, not the part. Second, label each piece in chalk or pencil the moment it comes off the saw; on a two-sheet job the shelves and stretchers go anonymous fast, and re-measuring eight near-identical rectangles costs more time than the optimizer saved. Full sheets are also the one place to bend the rip-first rule: if a 4×8 is too heavy to run over the table saw safely, make the first breakdown cut wherever it divides the sheet into two liftable halves, then follow the sequence.

Kerf, trim, and what “usable area” means

• Kerf is the material the blade turns to sawdust — 1/8″ for a typical full-kerf blade. The optimizer charges it to the right and bottom of every part.
• Edge trim shaves all four sides before packing — use 1/4″–1/2″ if your sheets arrive with dinged or out-of-square factory edges.
• Utilization and waste are figured against the post-trim usable area, and always sum to 100%. Waste includes kerf loss and unusable offcuts.