Kerf Calibration GeneratorFREE
Measure the real kerf of your laser on any material. Cut the file, find the narrowest slot that fully released, divide by two to get your kerf. Apply it in LightBurn or xTool Creative Space so press-fits and finger joints actually fit.
Materials worth calibrating
Kerf changes with material. Re-run the test whenever you switch. These three cover most laser work.
Frequently asked questions
What is laser kerf and why do I need to measure it?
Kerf is the width of material removed by the laser beam during a cut. It's usually between 0.08mm and 0.4mm depending on your laser, lens, and material. If you design a 50mm-wide part, the actual cut piece will be 50mm minus the kerf, so two pieces that should fit together end up loose. Knowing your kerf lets you compensate in software (LightBurn's Kerf Offset, xTool's Cut Offset) so press-fits and finger joints actually fit.
How do I use the kerf test file?
Download the SVG and cut it on the material you want to calibrate, at your normal cut settings. The sheet has a wedge of progressively wider slots labeled in millimeters. After cutting, find the narrowest slot that fully released. That slot width is approximately twice your kerf (material removed from both sides of the slot). Divide by two and you have your kerf.
Does kerf change between materials?
Yes, significantly. Kerf on 3mm basswood might be 0.15mm; on 3mm acrylic the same laser may produce 0.25mm because the beam melts a wider channel. Run a fresh test every time you switch material or thickness. Same laser, same settings, different material = different kerf.
Will kerf change with speed and power?
Yes. Higher power, slower speed, and more passes all widen the kerf because more material vaporizes. If you care about accuracy, always calibrate at the exact speed/power/pass count you use for production work. If you tune settings with our test-grid tool, re-run the kerf test after you lock them in.
What range should I pick?
Fine (0.05–0.3mm) is right for CO2 lasers on thin acrylic, Mylar, and paper. Medium (0.1–0.5mm) covers most diode and CO2 wood cuts. Coarse (0.2–0.8mm) is for thick material, multi-pass cuts, or older lasers with wider beams. If you have no idea, start with Medium.
How do I apply the kerf value in my software?
LightBurn: set Kerf Offset on your cut layer to half the kerf (it expands the path outward by that amount so the cut matches the drawn size). xTool Creative Space: use Offset in the object menu. For finger joints and press-fits, design with exact dimensions and let the software compensate. Don't bake the offset into your file.
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