What is kerf?

Kerf is the width of material a saw blade destroys on every cut. Push a 3 mm blade through a bar and the two parts you're left with are 3 mm shorter in total than what you started with. Every real cutting plan has to account for it.

Typical kerf widths

Saw / blade	Typical kerf
Drop saw / mitre saw blade	2, 3 mm
Thin-kerf timber blade	1.6, 2 mm
Metal cut-off disc	1, 2 mm
Cold saw (steel)	2, 2.5 mm
Bandsaw	0.8, 1.5 mm
1/8" table saw blade	3.2 mm (1/8")
Shear, guillotine, snap cutter	0 (nothing lost)

How to measure your kerf

Make one cut through scrap, push the two parts back together and measure how much shorter the pair is than before, or simply measure the width of the slot the blade leaves. Blade packaging usually lists it too, marked as kerf or cut width.

Why it matters: cut ten 500 mm parts from a 5 m bar with a 3 mm blade and you don't get ten parts. The nine cuts between parts eat 27 mm, so the last piece comes up 27 mm short. A cutting plan that ignores kerf is a plan for scrapping your last piece on every bar.

Kerf in a cutting plan

Our free cut list optimiser allows one kerf between every pair of parts automatically, and one at each end when you switch on end trim for rough or painted stock. Angled cuts consume more than square ones (the cut crosses the material diagonally), and the plan accounts for that too. Kerf is a free setting here; some tools paywall it, which means their free plans are physically wrong.

FAQ

Should I set kerf to zero?

Only for cutting methods that destroy no material: shears, guillotines, pipe snap cutters. For any spinning blade, measure it and set it.

Does kerf count as waste?

Yes. The plan reports it inside the saw component of each bar's waste, separate from the leftover remnant.

What about laser or plasma cutting?

Same idea, usually called the kerf there too: typically 0.1 to 0.5 mm for laser and 1 to 3 mm for plasma. Enter whatever your process removes.