Laser kerf is the width of material removed by the cut. If the programmed path follows the nominal geometry centerline, an outside part becomes undersized and an internal opening becomes oversized. Kerf compensation offsets the path by half the measured kerf toward the scrap side.
One-side path offset = measured kerf ÷ 2
Move external profiles outward; move hole and slot paths inward. Confirm how your CAM or laser software defines positive and negative offset before cutting.
Measure the process, not a generic table
Kerf changes with material, thickness, focus, nozzle, assist gas, power, speed, beam condition, and machine setup. Cut a test pattern with the same material and settings planned for production. A multi-cut coupon can make a small kerf easier to measure by accumulating several cut widths.
External profiles vs internal features
For an outside part, the retained material is inside the contour, so the beam centerline moves outward into the surrounding scrap. For a hole or slot, the retained material is outside the feature, so the centerline moves inward into the removed slug or opening.
| Feature | Path direction | Nominal centerline result |
|---|---|---|
| External profile | Outward by k/2 | Part undersized |
| Hole or slot | Inward by k/2 | Opening oversized |
Worked dimension example
Target an external square width of 50.000 mm with measured kerf 0.200 mm. Half kerf is 0.100 mm per side, so the beam-center path envelope becomes 50.000 + 0.200 = 50.200 mm. For a 20.000 mm hole with the same kerf, the path diameter becomes 20.000 − 0.200 = 19.800 mm.
The entered software offset may be 0.100 mm, not 0.200 mm, because most tools ask for the one-side offset. Always check the program’s convention and preview.
Test fit and process control
- Measure kerf using the production material, thickness, focus, gas, speed, and power.
- Confirm closed contours and inside/outside recognition in the CAM preview.
- Leave enough nesting space for the offset path.
- Use a test fit for tabs, slots, press fits, and assemblies.
- Track kerf after nozzle, optics, focus, material batch, or parameter changes.
- Do not use scaling as a substitute for a contour offset.
Technical references
Published and formula-checked by MfgWorkbench. Last reviewed September 15, 2026. See our editorial method.