What is kerf in laser cutting?

ForEducators · Researchers · Students

Updated 1 October 2026 Sources checked · Not externally reviewed

Short answer

Kerf is the width of material removed along a cut. If a laser follows a vector centerline without compensation, the finished edge falls roughly half the kerf width to each side of that path. An outside profile can therefore become smaller than drawn, while an internal opening can become larger.

Kerf: the beam removes a channel of material centered on the programmed line Two parts. On the left, a cross-section through a sheet shows a channel of material removed by the cut. A dashed line marks the programmed path and runs down the middle of that channel, so half the removed width lies on each side of it. The channel is slightly wider at the top than at the bottom, so the measured width depends on where through the thickness it is taken. On the right, two small figures show the consequence: for an outside profile the finished part is smaller than the drawn shape, and for an internal opening the finished hole is larger than the drawn shape. Dashed outlines are what was drawn, solid outlines are what comes out. The channel width is exaggerated for legibility. kerf at the top the programmed line half the width is lost each side of it Outside profile comes out smaller Opening comes out larger drawn actual
The channel width is exaggerated here — a real kerf is closer to a hairline. Note the slight taper: the channel is wider at the top than the bottom, which is why “what is the kerf” has no single answer even on one cut. Kerf is a measured result, not a number you can look up for a machine — it moves with material, thickness, focus, delivered energy, motion, assist and optics condition. Measure it on the stock you are actually cutting.

Kerf is a measured process result, not a universal number for a machine. It can change with material and thickness, focus, power and speed, and where it is measured through the thickness. For dimensional work, measure kerf on representative stock using the approved local process rather than borrowing a value from an unrelated settings table.

Sources

  1. LightBurn Software (laser control software documentation)Kerf – What it is and How to Compensate (LightBurn 2.2 User Guide)Defines kerf as the gap the beam removes from both sides of the path, explains why uncompensated parts come out undersized and slots oversized, and notes that kerf varies with material, thickness, speed and power. Software documentation, not a machine specification. Link checked September 2026.
  2. Rayforge (open-source laser control software documentation)Kerf CompensationShows the finished edge sitting half the kerf width from the tool path, with a worked 0.4 mm / 0.2 mm example, and names focus and cut settings among what changes kerf. Software documentation from one open-source project. Link checked September 2026.
  3. Harvard Graduate School of Design Fabrication Lab (academic laser-cutter training documentation)Laser Training ChecklistOne university fab lab's training checklist: kerf can vary between machines, settings and materials, so measure a test cut in the material you will use rather than relying on posted values. Link checked September 2026.
  4. Moradi et al., Applied Sciences (peer-reviewed, open-access research paper)Capability Enhancing of CO2 Laser Cutting for PMMA Sheet Using Statistical Modeling and Optimization (Appl. Sci. 2023, 13(23), 12601)A measured experiment showing how cutting settings and focus change kerf, including the difference between the top and bottom of the cut. One material and thickness only (5 mm acrylic, CO2 laser). Link checked September 2026.

Sources are checked by Laser TeamWork, not by an outside expert. General guidance: your machine’s manual and your school’s procedures come first. Report a correction.

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