Saw blade kerf explained — a plain-English guide for cutting-list work

If you have ever cut a stack of shelves from a sheet of plywood and ended up with the last shelf 5 mm too narrow, you have already met kerf in person — even if nobody told you its name. Kerf is the width of material the blade removes on every cut. It is small, it is boring, and if you ignore it your parts come out short. This guide walks through what kerf is, how much it costs you per sheet, and how to get the number right for your saw.

What kerf actually is

A saw blade is not infinitely thin. The teeth are wider than the body of the blade so it does not bind in the cut, and that width is what the blade grinds away as it passes through the wood. That gap left behind is the kerf. On a typical panel saw the kerf is about 3 mm; on a fine track-saw blade it can be as little as 2.2 mm; on a 6 mm CNC router bit it is a full 6 mm.

The important thing to understand is that every cut takes away kerf from something. If you draw two 600 mm shelves side by side on a sheet and cut between them, one of them ends up 597 mm, or both end up 598.5 mm, depending on where your mark was. Multiply that across a full cutting list and by the time you get to the last part on the sheet you can be 15–20 mm short.

Why cutting-list optimizers care

A cutting-list optimizer like OptimalLayout does not just pack rectangles — it packs rectangles with a gap between them. That gap is your kerf. Set the kerf too small and the optimizer will fit an extra part on the sheet that will not actually fit once you cut. Set it too big and the optimizer wastes a strip you could have used.

On a full 2440 × 1220 mm sheet, changing the kerf from 2 mm to 4 mm typically costs you one usable strip of material — often the difference between fitting all your parts on one sheet and needing a second. Getting the number right is worth a few minutes.

Typical kerf values by tool

• Industrial vertical panel saw (Striebig, Holzher): 3.2 – 4.4 mm
• Sliding table saw (Altendorf, SCM, Felder): 3.0 – 3.5 mm
• Beam saw / CNC panel saw: 3.8 – 4.8 mm
• Track saw (Festool TS 55/75, Mafell, Makita SP): 2.2 – 2.5 mm
• Cabinet table saw, full-kerf blade: 3.0 – 3.2 mm
• Cabinet table saw, thin-kerf blade: 2.0 – 2.4 mm
• Contractor / job-site table saw: 2.4 – 3.0 mm
• Compound mitre saw: 2.0 – 3.0 mm
• Circular saw with rip blade: 1.8 – 2.5 mm
• Jigsaw (T-shank wood blade): 1.0 – 1.8 mm
• Band saw (¼" to ½" blade): 0.8 – 1.2 mm
• Scroll saw: 0.4 – 0.8 mm
• CNC router, 6 mm compression bit: 6 mm
• CNC router, 3 mm bit: 3 mm
• Laser cutter (plywood, 3–6 mm): 0.1 – 0.3 mm

These are ranges, not gospel. The exact number depends on the specific blade, its tooth geometry, whether it is new or dull, and how much side play the arbor has. If accuracy matters, measure your own — see below.

Why 3 mm is the OptimalLayout default

We ship with a 3 mm default because it matches the panel saws and full-kerf table saws that most working cabinet shops use, and it is safe: if your real kerf is smaller, you get a little extra yield; if your real kerf is larger you have not overcommitted the sheet.

If you know you use a track saw or a thin-kerf blade, drop it to 2.4 mm and you will typically squeeze one or two extra small parts per sheet. If you cut on a CNC router, set the kerf equal to the bit diameter.

How to measure your own kerf in 60 seconds

1. Take a piece of scrap at least 200 mm long.
2. Measure it with callipers and write down the length.
3. Make a single cut roughly in the middle. Do not move the piece.
4. Measure the two halves and add them together.
5. The difference between the original length and the sum of the halves is your kerf.

Example: 200.0 mm scrap, cut in half, halves measure 99.4 mm and 97.8 mm. Total 197.2 mm. Kerf = 200.0 − 197.2 = 2.8 mm. That is the number to type into the optimizer.

Common kerf mistakes

• Forgetting the first cut. The very first cut on a fresh sheet also removes kerf. OptimalLayout accounts for this automatically — you can measure straight from the diagram — but if you are drawing your own layout on paper, subtract kerf from the sheet edge too.
• Cutting all one direction first. If you rip a sheet into strips and then crosscut, the kerf on the rip cuts subtracts from the length of every part in that strip. Optimizers assume this; hand-drawn layouts often do not.
• Mixing blade types on one project. If you break down a sheet with a track saw and then finish on the table saw, use the larger of the two kerfs when planning, or split the layout into two stages.
• Assuming the blade has not dulled. A dull blade wobbles, and a wobbling blade cuts a wider kerf. If you have not changed the blade in six months, measure again.

Kerf and pricing

Kerf is not just an accuracy issue — it is a materials cost. On a €80 sheet of 18 mm birch ply, one wasted strip is €8 in the bin. Across a kitchen with six sheets, getting the kerf right can be €30–€50 back in your pocket. That is why we treat the kerf field as the single most important input in the optimizer after the sheet size itself.

Bottom line

Measure your kerf once, write it on a piece of tape stuck to your saw, and use that number every time you plan a cut list. If you are not sure, start with 3 mm — it is a safe default that will not leave you with parts too small to use.

Next steps. Head over to the optimizer and enter your real kerf value, or read our guide on how cutting-list optimization actually works to see why the algorithm cares so much about that one number.

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