Maker and DIY Calculators

Laser kerf compensation.

A laser burns away a thin strip, the kerf, so parts come out smaller than drawn and holes come out larger. Enter the size you want and your kerf to see what to draw, or measure your kerf from a test cut.

Draw a part at target + kerf and a hole or slot at target - kerf. The path is offset by kerf / 2 on each side. With a 0.2 mm kerf, a 50 mm part is drawn 50.20 mm and a 10 mm hole is drawn 9.80 mm.

Size and kerf

Finished size you want

The size of the part, or of the hole or slot, after cutting. Any unit works if you use it throughout.

Feature

Kerf width

The width of material the beam removes. Measure it on your own material (below) rather than assuming.

Pieces side by side For a row of parts cut from one sheet, to see the total width kerf takes.

Test cut: size you drew

Optional. To measure kerf, cut a test square or hole of known drawn size.

Test cut: size you measured

Measure with calipers.

Test cut feature

Compensation

Fill the form and press Calculate.

Worked example

A 50 mm part with a 0.2 mm kerf is drawn at 50 + 0.2 = 50.20 mm, so the path sits 0.1 mm outside the 50 mm outline on each side. Drawn at exactly 50 mm it would come out 49.80 mm. A 10 mm hole is drawn at 10 - 0.2 = 9.80 mm (drawn at 10 mm it would be 10.20 mm). Ten parts side by side lose 10 x 0.2 = 2.0 mm to kerf. To measure kerf, cut a 50 mm square and find it measures 49.8 mm: kerf = 50 - 49.8 = 0.2 mm.

How it works

The beam is centred on the drawn line and removes half a kerf on each side. For an outside edge, the part is the material left inside the cut, so it ends up one kerf smaller than drawn. For a hole or slot, the opening is the removed region, so it ends up one kerf larger. Compensating means moving the path by kerf / 2 away from the part on outside edges and into the hole on inside edges.

Kerf in laser cutting is the width of material burned away; it depends on the laser and the material. Measure it by cutting a test square (kerf = drawn - measured) or a test hole (kerf = measured - drawn), ideally on the material and thickness you will use. For snug joints such as finger joints, test a few sizes since material, finish and glue also matter.

Sources (opened 2026-10-08). What Is Kerf in Laser Cutting? - SendCutSend (Feb 24, 2023) for the definition of laser kerf as the material burned away, and that it depends on the laser and material. The offset-by-half-kerf rule and the measurement method are our own geometry, not a published standard.

FAQ

What is kerf in laser cutting?

Kerf is the width of material the laser beam burns away along the cut. It varies with the laser and the material being cut.

How do I compensate for kerf?

Offset the cut path by half the kerf on each side: outward for the outside of a part, inward for a hole or slot. Equivalent: draw a part at target plus kerf and a hole at target minus kerf.

How do I measure my kerf?

Cut a test square of known drawn size and measure it with calipers: kerf is drawn minus measured. For a hole, kerf is measured minus drawn. Use the same material and settings as your real job.

Do I need kerf compensation for engraving or scoring?

No. Kerf matters only for cut-through edges that must meet a target size or fit another part.

Is kerf the same for all materials?

No. Different materials, thicknesses, speeds, power and focus change the kerf, so re-measure when they change.

Disclaimer

Estimates from the numbers you enter. Always make a test cut on your material before cutting expensive stock.