What are "kerf" and tolerances in laser cutting? (cutting loss)

What is the kerf in laser cutting – and why should you consider it?

If you're working with laser cutting for the first time, it might seem like the laser cuts exactly what you draw. But in reality, a small amount of material always disappears during cutting. We call this the kerf. In this blog, we explain what the kerf is, how large it usually is, and what the implications are for your design and fit.

What is the kerf?

The kerf is the width of the cut path: the material that the laser actually removes during cutting. In laser cutting, this is usually very narrow – somewhere between 0.05 and 0.3 mm, depending on the material, the lens, the power, and the focus. This means that the contour of your design always shifts slightly inward.

How large is the kerf in our materials?

At Laser Cut Supply, we only provide materials suitable for laser cutting: flat, clean, and with consistent composition. This makes the kerf in our materials highly predictable. For most materials, this is 0.2mm, but for thicker materials (8mm+), it can be slightly more, and for low-density materials like hard foam and soft foam, the kerf is much larger, usually around 1mm.

Note: the exact value depends on your settings. Always test with your own machine.

Why is the kerf important for your design?

In some designs, a tenth of a millimeter doesn't make much difference. But if you want parts to click together tightly – like in a box, holder, or puzzle – then the kerf is crucial.If you do nothing, it might be that:

• parts are too loose (too much play)
• connections don't fit or wobble
• press fits are too tight or even break during assembly

How do you compensate for the kerf?

There are two ways to account for the kerf:

• In your design: Pull contours inward or outward by half the kerf width. For example: do you want a hole of exactly 10 mm? Then draw it 10.2 mm large if your kerf is 0.2 mm.
• In your software or plugin: Some CAM or plugin tools (like Inkscape’s Boxmaker) allow you to enter a kerf value that is automatically included in the calculation.

Summary

• The kerf is the material loss due to the width of the laser cut
• Usually, this is around 0.2 mm
• For parts that need to fit precisely, you need to adjust the kerf
• This can be done through your design or with settings in your software

Do you want materials that cut predictably and cleanly, with a stable kerf? Then you're in the right place with Laser Cut Supply. Our sheets are flat, laser-ready, and tested for consistent quality – so you don't have to guess.