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 post, 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 a consistent composition. This makes the kerf in our materials highly predictable. For most materials, this is 0.2 mm, but for thicker materials (8 mm+), it can be slightly wider. For low-density materials like hard foam and soft foam, the kerf is much larger, usually around 1 mm.

Please 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, you might find 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: Offset contours inward or outward by half the kerf width. For example: do you want a hole of exactly 10 mm? Then draw it 9.8 mm in size if your kerf is 0.2 mm. Conversely, if you want a 10 mm disc, draw it 10.2 mm in size.
• 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 must compensate for the kerf
• This can be done in your design or using settings in your software

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