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Laser kerf calculator

Cut one test square, measure it, and get your kerf, the offset per edge and the slot width for a press fit.

What does the cut square measure?Callipers on the piece, not the hole. Both directions, use the average.mm

Typical kerf · Plywood 3 mm

0.18 mm

What the beam removes, full width.

Offset per edge

0.09 mm

Grow outlines, shrink holes by this. xTool Studio's kerf offset takes this number.

Press-fit slot

2.82 mm

Draw it this wide for 3 mm material: it comes out at 3 mm.

Loose slot

3.10 mm

Glued joints and easy assembly.

Thinnest feature

0.96 mm

Anything narrower burns away or snaps.

Every cut edge moves inward by 0.09 mm. A drawn 20 mm square comes out 19.82 mm; a drawn 20 mm hole comes out 20.18 mm.

Showing a typical value until you type a measurement.

Quick answer

What is kerf in laser cutting?

Kerf is the width of material the laser beam burns away along a cut. On hobby lasers it is usually 0.1 to 0.3 mm. Because the beam is centred on the line, each edge moves by half the kerf: a square drawn 20 mm with a 0.2 mm kerf comes out 19.8 mm, and a 20 mm hole comes out 20.2 mm.

How it works

Cut the test square
Download the 20 mm calibration square and cut it from the material you are going to use, with the settings you are going to use.
Measure the piece
Measure the square that fell out with callipers, not the hole it left. Take both directions and use the average.
Type both numbers
Enter the size you drew and the size you measured. The kerf is the difference.
Use the results
Grow outside shapes and shrink holes by the offset per edge, and draw slots at the press-fit width so parts hold without glue.

Typical kerf by laser and material

Typical laser kerf in millimetres by laser type, material and thickness
Laser	Material	Thickness	Kerf
xTool D1 Pro 20 W	MDF	3 mm	0.15–0.20 mm
xTool D1 Pro 20 W	MDF	6 mm	0.18–0.25 mm
xTool D1 Pro 20 W	Birch plywood	3 mm	0.15–0.20 mm
xTool D1 Pro 20 W	Birch plywood	6 mm	0.20–0.28 mm
xTool D1 Pro 20 W	Acrylic, opaque	3 mm	0.12–0.18 mm
xTool D1 Pro 20 W	Corrugated cardboard	3 mm	0.20–0.30 mm
xTool D1 Pro 10 W	MDF	3 mm	0.12–0.18 mm
xTool D1 Pro 10 W	Birch plywood	3 mm	0.12–0.18 mm
xTool D1 Pro 10 W	Corrugated cardboard	3 mm	0.18–0.28 mm
xTool P2 / P2S 55 W CO2	MDF	3 mm	0.15–0.20 mm
xTool P2 / P2S 55 W CO2	MDF	6 mm	0.18–0.22 mm
xTool P2 / P2S 55 W CO2	Birch plywood	3 mm	0.15–0.20 mm
xTool P2 / P2S 55 W CO2	Acrylic, clear	3 mm	0.12–0.18 mm
xTool P2 / P2S 55 W CO2	Acrylic, opaque	3 mm	0.12–0.16 mm
Diode laser, about 20 W	MDF	3 mm	0.15–0.22 mm
Diode laser, about 20 W	MDF	6 mm	0.20–0.28 mm
Diode laser, about 20 W	Birch plywood	3 mm	0.15–0.20 mm
Diode laser, about 20 W	Birch plywood	6 mm	0.20–0.28 mm
Diode laser, about 20 W	Acrylic, opaque	3 mm	0.12–0.20 mm
Diode laser, about 20 W	Corrugated cardboard	3 mm	0.20–0.32 mm
Diode laser, about 20 W	Leather	3 mm	0.18–0.28 mm
CO2 laser, about 40 W	MDF	3 mm	0.18–0.25 mm
CO2 laser, about 40 W	MDF	6 mm	0.22–0.30 mm
CO2 laser, about 40 W	Birch plywood	3 mm	0.18–0.25 mm
CO2 laser, about 40 W	Birch plywood	6 mm	0.22–0.28 mm
CO2 laser, about 40 W	Acrylic, opaque	3 mm	0.12–0.20 mm
CO2 laser, about 40 W	Acrylic, clear	3 mm	0.15–0.22 mm
CO2 laser, about 40 W	Corrugated cardboard	3 mm	0.22–0.35 mm
CO2 laser, about 40 W	Leather	3 mm	0.18–0.28 mm

Ranges compiled by the laser-cutting community (source: Box Studio kerf reference table). A table is where you start; the square you cut this morning is the number. Slower speed, more power, a dirty lens and poor focus all widen the kerf.

The formulas

Kerf: drawn size − measured size of the piece
Offset per edge: kerf ÷ 2
Press-fit slot: material thickness − kerf
Loose slot: material thickness + 0.1 mm
Thinnest feature: 2 × kerf + 0.6 mm
Hole for a pin: pin diameter − kerf

Questions makers ask

How do I measure my laser's kerf?

Cut a square of a known size, for example 20 mm, from the material and with the settings you plan to use. Measure the piece with callipers. Kerf = drawn size − measured size. A 20 mm square that measures 19.82 mm means a kerf of 0.18 mm. Repeat whenever the material, the lens, the focus, the speed or the power changes.

What is a typical kerf for a diode or CO2 laser?

Community reference values put a 20 W diode laser at about 0.15–0.22 mm in 3 mm MDF or plywood and 0.12–0.20 mm in 3 mm opaque acrylic, and a 40 W CO2 laser at about 0.18–0.25 mm in 3 mm MDF or plywood. Slower speed, more power, a dirty lens or poor focus all widen it, so treat a table as a starting point and measure your own.

Is kerf the full width of the cut or half of it?

Kerf is the full width the beam removes. Some guides divide the measured difference by two and call that the kerf; that half is really the offset per edge, the distance each edge moves. This calculator shows both so there is no doubt: kerf is what the beam eats, the offset is what you compensate each edge by.

What do I type into xTool Studio's kerf offset field?

Half of your kerf. xTool Studio's kerf offset moves the beam sideways from the line, so it takes the offset per edge: for a 0.18 mm kerf enter 0.09 mm. It works on closed shapes only, and a positive value moves the beam outward.

How wide should a slot be for a press fit?

Draw the slot as the material thickness minus the kerf. The laser widens every slot by one kerf, so a 3 mm sheet with a 0.18 mm kerf needs a slot drawn 2.82 mm to come out at 3.00 mm. Measure the sheet first: 3 mm plywood is often 2.7 to 3.2 mm.

What is the smallest detail a laser can cut?

A feature has to survive a kerf on both sides and still hold together when handled. This calculator uses two kerfs plus 0.6 mm as the thinnest feature worth drawing, which is about 1 mm for a 0.2 mm kerf in plywood.

Do I need an account, and is my data uploaded?

No account and nothing uploaded. The calculation and the test square are made in your browser.

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