Laser Cut Box Generator with Kerf Compensation

Set the box size, the sheet thickness and your laser's kerf, then download the SVG.

Your measurements

Enter the outside size of the box and your sheet. Everything updates as you type.

Material

Sheet material3 mm nominal

Measured sheet thickness

Measure with calipers. Sheets are often a little off their nominal thickness, and the finger depth uses this number.

Box (outside size)

Common sizes (mm)

Length

Width

Height

Laser

Laser type

Sets the kerf to 0.12 mm, a typical starting value for this material. Test-cut and measure your own for a tight fit.

Inside114 × 74 × 54 mm

Space inside the finished box

114 × 74 × 54mm

= 4.49" × 2.91" × 2.13"

Length × width × height inside the walls. The cut file draws six finger-jointed panels for the outside size you entered.

Kerf compensation: +0.06mm per edge; Half of the 0.12 mm kerf
Sheet area needed: 400 × 190mm; All six panels laid out with spacing

Panels are drawn at their finished size. The file moves every cut line out by 0.06 mm to allow for the kerf.

Panel sizes

The six parts as they are laid out in the cut file.

Panel	Size	In inches	Fingers
Top	120 × 80 mm	4.72" × 3.15"	11 × 7
Bottom	120 × 80 mm	4.72" × 3.15"	11 × 7
Front	120 × 60 mm	4.72" × 2.36"	11 × 5
Back	120 × 60 mm	4.72" × 2.36"	11 × 5
Left	80 × 60 mm	3.15" × 2.36"	7 × 5
Right	80 × 60 mm	3.15" × 2.36"	7 × 5

The SVG is in millimetres. Import it into LightBurn, xTool Creative Space, Glowforge or Inkscape, check that the size reads correctly, and set the red lines to cut.

How this was calculated

Kerf, inside size and fingers, with your numbers.

Step 1: Kerf
kerf = width of material the beam removes
= 0.12 mm (typical starting value for Baltic Birch Plywood 3mm (1/8") on a 20–40 W diode)
= 0.12 mm
Measure yours: cut a row of identical squares, push them together, and divide the gap left over by the number of cuts.
Step 2: Half-kerf offset
offset = kerf ÷ 2
= 0.12 ÷ 2
= +0.06 mm on each edge
Each cut edge loses half the kerf, so every cut line is moved outward by that amount and the parts come out at their drawn size.
Step 3: Inside of the box
inside = outside − 2 × sheet thickness
= 120 − 2 × 3, 80 − 2 × 3, 60 − 2 × 3 mm
= 114 × 74 × 54 mm
The sizes you enter are outside sizes. Each wall takes up one sheet thickness on both sides.
Step 4: Fingers per edge
fingers = edge ÷ 12 mm target, rounded to an odd number (at least 3)
= 120 mm → 11, 80 mm → 7, 60 mm → 5
= 10.91, 11.43 and 12 mm wide
An odd count puts a finger at both corners. Fingers are kept at least 4.5 mm wide (1.5 × thickness, minimum 3 mm) so they do not snap.

Sources

Baltic Birch Plywood 3mm (1/8"): nominal thickness and kerf starting values
Estimated
Typical value, not from a maker's document. Measure or confirm before relying on it.

In short

Offset each cut line by half the kerf. For Baltic Birch Plywood 3mm (1/8") with a typical 0.12 mm diode kerf that is +0.06 mm per edge.

Material presets load a typical thickness and starting kerf; replace them with your own measurements for a tight fit.

Starting kerf by material and laser (estimates)

Typical starting values only; kerf depends on focus, power, speed and the exact sheet. Measure your own with a test cut.

Material	Thickness	10 W diode	20 W diode	40 W CO₂	80 W CO₂
Baltic Birch Plywood 3mm (1/8")	3 mm	0.14 mm	0.12 mm	0.15 mm	0.18 mm
Cast Acrylic Sheet 3mm (1/8")	3 mm	0.2 mm	0.15 mm	0.12 mm	0.14 mm
MDF Board 3mm (1/8")	3 mm	0.15 mm	0.13 mm	0.16 mm	0.19 mm
Basswood Plywood 3mm	3 mm	0.12 mm	0.1 mm	0.13 mm	0.16 mm
Baltic Birch Plywood 6mm (1/4")	6 mm	0.22 mm	0.18 mm	0.2 mm	0.24 mm

Worked example: 120 × 80 × 60 mm box in Baltic Birch Plywood 3mm (1/8")

How the kerf offset and panels are worked out.

Step 1: Kerf
kerf = width of material the beam removes
= 0.12 mm (typical starting value for Baltic Birch Plywood 3mm (1/8") on a 20 W diode)
= 0.12 mm
Measure yours: cut a row of identical squares, push them together, and divide the gap left over by the number of cuts.
Step 2: Half-kerf offset
offset = kerf ÷ 2
= 0.12 ÷ 2
= +0.06 mm on each edge
Each cut edge loses half the kerf, so every cut line is moved outward by that amount and the parts come out at their drawn size.
Step 3: Inside of the box
inside = outside − 2 × sheet thickness
= 120 − 2 × 3, 80 − 2 × 3, 60 − 2 × 3 mm
= 114 × 74 × 54 mm
The sizes you enter are outside sizes. Each wall takes up one sheet thickness on both sides.
Step 4: Fingers per edge
fingers = edge ÷ 12 mm target, rounded to an odd number (at least 3)
= 120 mm → 11, 80 mm → 7, 60 mm → 5
= 10.91, 11.43 and 12 mm wide
An odd count puts a finger at both corners. Fingers are kept at least 4.5 mm wide (1.5 × thickness, minimum 3 mm) so they do not snap.

Laser cut boxes: common questions

Kerf, test cuts and sheet thickness.

What is kerf and why does it matter for a laser cut box?

Kerf is the width of material the laser burns away. Without compensation every finger is slightly too small and every slot slightly too big, so joints are loose. Entering your kerf makes the generator offset the cut lines so the joints press together.

How do I measure my laser's kerf?

Cut a strip of ten 10 mm squares from the sheet you will use, push the pieces together, and measure the total length. The difference from 100 mm divided by the number of cuts is your kerf. Repeat whenever you change material, focus, power or speed.

What sheet thickness should I enter?

The real thickness measured with calipers, not the nominal size. Plywood sold as 3 mm or 1/8" is often a few tenths of a millimetre off, and the finger depth is set from this value.