Use the actual cut width
Blade labels and tooth geometry do not replace a test cut. Measure a representative cut in suitable scrap using the intended setup and record the assumption with the project. Recheck after changing the blade or process.
Count kerf by operation
For a sequence of adjacent pieces cut from one blank, kerf occurs between cuts, not as a percentage of each finished piece. Model ripping and crosscutting separately because the number of cuts and setup may differ.
In a classic end-grain board, rip kerf affects the first-panel stock. Crosscut kerf affects the slice yield and therefore the required first-panel length.
Keep kerf separate from other loss
- End cleanup before or after a cut sequence.
- Jointing and planing allowance.
- Final squaring and trim.
- Flattening of the glue-up.
- Profiles and grooves.
- Defects and unusable stock.
Kerf is deterministic only when the cut sequence is known. A general waste factor cannot show which operation consumed the material.
Verify the yield
Lay out the blank length as end trim + pieces + kerfs + end trim. Confirm the total physically fits the prepared stock. After a test batch, compare actual yield with the plan and update the assumption rather than changing historical projects silently.