What is saw kerf, and why does it matter?
Last updated 23 October 2026
Kerf is the width of the cut a saw makes: the strip of board the blade turns into sawdust. It is only a few millimetres, but on a full sheet those millimetres add up, and they decide whether the last part fits.
Kerf in one picture
Cut a 1000 mm board in half with a 3 mm blade and you don’t get two 500 mm pieces. You get two pieces that add up to 997 mm: 3 mm left the board as dust. Each extra cut costs another blade width.
The word comes from Old English cyrf, a cutting. It is also where this site gets its name.
Typical kerf by saw
These are typical figures. Blades differ, and the set of the teeth (how far they bend outwards) changes the real width, so measure your own.
| Saw and blade | Typical kerf |
|---|---|
| Table saw, full-kerf blade | 3.2 mm (1/8") |
| Table saw, thin-kerf blade | 2.4 mm (3/32") |
| Track saw / plunge saw | 2.2 to 2.8 mm |
| Circular saw (184 mm / 7¼") | 2.0 to 2.8 mm |
| Panel saw or beam saw at a board supplier | 3.2 to 4.4 mm |
| Band saw | 0.6 to 1.2 mm |
How to measure your kerf
- Take an offcut with one straight edge and measure its width with a vernier or digital caliper.
- Rip it roughly in half, with the blade set to the height you normally cut at.
- Measure both pieces. The original width minus the two pieces is your kerf.
Measuring the slot directly works too, but a caliper in a narrow slot tends to read a little small.
How kerf changes a cut list
Say you are cutting shelves from a 2750 mm board. You trim 10 mm off each end to get clean, square edges, which leaves 2730 mm. With a 3.2 mm blade:
- Six shelves at 450 mm: 2700 mm of shelf plus five cuts between them (5 × 3.2 = 16 mm) is 2716 mm. They fit.
- Six shelves at 453 mm: 2718 + 16 = 2734 mm. The sixth shelf comes up 4 mm short, and you need another board.
On paper both jobs look the same. The kerf is the difference, which is why it belongs in the layout and not in your head. Kerf (the app) adds the blade width between neighbouring parts and the edge trim around each sheet, so every layout still works once the dust settles.
Kerf and board suppliers
If your supplier cuts the boards, their beam saw has its own kerf, and they will lay the parts out themselves. Send finished part sizes, not sizes with kerf added. Kerf’s supplier cutting list does exactly that, while the layout it shows you uses the kerf you set, so your estimate of how many boards to buy stays realistic.
Common questions
What does kerf mean?
Kerf is the width of the slot a saw blade cuts. The wood in that slot turns to sawdust, so every cut makes your pieces slightly shorter in total than the board you started with.
How wide is a table saw kerf?
A full-kerf table saw blade cuts about 3.2 mm (1/8 inch). Thin-kerf blades cut about 2.4 mm (3/32 inch). Measure your own blade with a test cut, as the set of the teeth varies.
Should a cut list include the kerf?
Your part sizes should be the finished sizes. The layout is what needs the kerf: a cut list optimiser adds one kerf between neighbouring parts so the pieces still fit on the board after every cut.
Next: how to make a cut list, or the board and sheet size guide.