Workshop guide · kerf width explained

Kerf Width Explained for Cut Lists and Sheet Layouts

Kerf is small on one cut and decisive across a tight row. A layout that ignores it can show parts fitting exactly where the real blade removes the material needed for the final piece.

Kerf width is the width of material removed by the blade during a cut. Measure it with the blade, machine and material planned for the job, then enter that value once as the layout kerf. Keep finished part dimensions unchanged; the kerf belongs between adjacent parts, not inside them.

Test a measured kerf in the layoutEnter finished part sizes and one measured kerf value; the browser tool reserves it between cuts.

Measure the cut instead of guessing from the label

Make a representative cut in scrap using the blade and setup planned for the project. Measure the original piece, then measure the two resulting pieces together. The difference is the material removed by that cut. Repeat if the result is hard to read and use a measuring method precise enough for the tolerances of the project.

A blade specification is a starting point, but the effective cut can depend on the blade, runout, setup and material. When a row is tight, use the measured result rather than a remembered default.

Measurement

kerf = original width − combined width of the two cut pieces

Put kerf between parts, not in part dimensions

A cut list should state the required finished width and length. The layout then allocates space between parts for each separating cut. If kerf is added to every part and also entered in the optimizer, the plan double-counts it and can overstate the stock required.

Edge trim is a separate allowance. Reserve damaged or out-of-square edges in the usable stock dimensions, then apply kerf only to the cuts that separate parts.

Check a tight row with simple arithmetic

For parts placed side by side in one uninterrupted row, add their widths and add kerf for the separating cuts. A row of n adjacent parts has n minus one separations before any extra edge trim or finishing cut. The same principle applies vertically using part lengths.

A full two-dimensional layout can contain different cut sequences, so use the arithmetic as a diagnostic rather than a replacement for the diagram. If the total is close to the usable stock dimension, verify the sequence and measurement before cutting.

Tight-row check

occupied span = sum of finished part widths + kerf × (number of adjacent parts − 1)

Recalculate when the cutting setup changes

Changing the blade or breakdown method can change the effective kerf and therefore the layout. Update the value and regenerate the diagram rather than editing individual part dimensions to make the old plan fit.

The free cut list optimizer applies one kerf value to the layout. Boardcut keeps kerf with the plan and supports larger projects with multiple material groups and ordered cut steps.

Questions

What is kerf width?

It is the width of material removed by a cut. It is not part of either finished piece.

Is kerf the same as blade thickness?

Not necessarily. The effective cut is what matters for the layout, so measure a representative cut made by the planned blade and setup.

How many kerfs are between four adjacent parts?

There are three separating cuts between four adjacent parts, before any edge trim or additional finishing cuts.

Can I set kerf to zero in a cut list optimizer?

Only if the real process removes no material. For a saw layout, zero kerf can create a diagram that cannot produce all entered finished dimensions.