How Kerf turns a cut list into a table-saw-ready layout

A 4x8 sheet of ¾" plywood runs $60 to $120 depending on the species. If your next project is a bank of shop cabinets, you're probably buying four or five of them. The difference between a smart layout and a hand-drawn one is often a whole sheet — enough to pay for a good blade or a new pair of dado inserts.

This post walks through what Kerf is actually doing when you hit Solve Layout — and why "eyeball it on graph paper" has been leaving real money on your shop floor.

The problem, in one sentence

Given a set of stock sheets (your raw 4x8s or 5x5 Baltic birch), a set of cut pieces you need for your project, and a saw kerf width, find an arrangement that uses as few sheets as possible without overlapping any pieces.

That's a 2D bin packing problem, and in the general case it's NP-hard — there's no known algorithm that always finds the optimal answer in reasonable time. For a real project with 40 cuts, brute force would take longer than the heat death of the universe.

So what do you do? You use a heuristic — a smart packing strategy that's provably not optimal, but gets within a few percent of optimal in milliseconds.

Why hand-drawn layouts waste wood

Here's what a typical hobbyist cut diagram looks like:

• Draw the sheet on graph paper.
• Start with the biggest piece in the top-left corner.
• Fit the next biggest piece somewhere it fits.
• Keep going until the sheet is full.
• Start a new sheet for what's left.

This is called first-fit decreasing, and it's the oldest heuristic in the book. It's fine. But it has a known blind spot: it only considers where the next piece goes, never what comes after that piece.

The real-world consequence: you end up with weird L-shaped scrap along the right edge of every sheet, because the algorithm kept stuffing tall pieces into a column and never looked back.

What Kerf actually does

Kerf implements three different packing strategies, and you pick the one that matches how your shop works.

1. Best Offcut (default)

Uses a variant of the MaxRects algorithm with Best Short Side Fit scoring. After every piece is placed, Kerf tracks the set of remaining rectangular free spaces on each sheet. For the next piece, it picks the free rectangle where the piece fits with the smallest leftover short side — which tends to preserve one large, reusable offcut instead of a handful of weird slivers.

This is the right default if you keep a scrap pile and don't want it turning into firewood.

2. Fewest Sheets

Same MaxRects engine, different scoring. This mode optimizes purely for total sheets used, packing as tightly as possible even if it leaves awkward remainders. It's the right call when plywood is expensive or hard to source, and you'd rather buy fewer sheets than preserve offcuts.

In testing, Fewest Sheets averages 4-12% fewer sheets than the default on projects with 20+ pieces.

3. Easiest Cuts

This is the strategy table-saw-only shops want. It uses a guillotine packer with an extra constraint: every cut must go all the way across the sheet, edge to edge.

No plunge cuts, no track saw, no "rip this part, then chop the middle." If you can only cut straight lines from one side of the sheet to the other, this is the only layout you can actually build.

Easiest Cuts uses slightly more material than Fewest Sheets, but every cut is a single pass through the saw. For a lot of hobbyists, that tradeoff is a no-brainer.

The kerf itself

The name of the app is also the thing that makes the math tricky.

A typical table-saw blade has a kerf of about ⅛". Every cut you make removes ⅛" of material. If you rip a 48" panel in half and forget about the blade, you end up with two pieces that are 23 15⁄16" wide, not 24".

Kerf tracks this automatically. You set your blade width once in Settings, and every piece placement accounts for it. This is the one bug that hand-drawn layouts produce over and over — "I measured it right, why are the drawer bottoms short?"

What you still have to do

Kerf does the packing. It doesn't know:

• Which face of the plywood has the clean veneer.
• Whether your sheet is actually 48.25" wide (it probably is).
• That you're out of ⅜" plywood and have to substitute ½".

You're still the woodworker. The app just handles the tedious part — the Tetris — so you can get to the shop faster.

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Download Kerf on the App Store to try all three strategies on your next project. Free, no account, no ads.