No need to know the vocabulary first
A few words, explained
- Kerf
- The width of material removed by a cut.
- Stock
- The wood or other material you start with.
- Joinery
- The methods used to connect pieces of wood.
- Cut list
- A list of the pieces you need, with their sizes and quantities.
- Trim allowance
- Extra material left so an end or edge can be cleaned up later.
Measure the blade, not the pencil line
Kerf is the width removed by the blade. A thin-kerf blade and a full-kerf blade remove different amounts, so use the blade that will actually make the cuts when planning a layout.
Count every separating cut
Each time a part is cut free, the blade consumes material. Add the blade kerf for every cut between parts, then add trim allowance when the stock needs to be squared or brought to final size.
Include cutting loss before laying out parts
Start with the finished part, add trimming room, then add kerf between adjacent parts. Test a short layout on scrap when parts are narrow, expensive, or repeated.
See it in an example
Four parts, three gaps
For a drawing exercise, divide a 1,000 mm board into four equal parts with three cuts. Each cut removes 3 mm. Both ends are already prepared and no extra trimming is needed. Real boards may need additional allowance.
| Step | Example | What it means |
|---|---|---|
| Wood before cutting | 1,000 mm | Measure the length available after preparing the ends. |
| Material removed | 3 cuts × 3 mm = 9 mm | Count the cuts in this particular layout. |
| Wood left for the parts | 1,000 − 9 = 991 mm | Subtract the cutting loss first. |
| Length of each equal part | 991 ÷ 4 = 247.75 mm | Four 250 mm parts would not fit this plan. |
Try it with your project
- Draw the full length of your prepared board.
- Mark each finished part and every cut needed to separate it.
- Add the widths lost to cutting and any extra trimming. Compare the total with the board you have.
Will four 250 mm parts fit the 1,000 mm board in this example?
No. The parts alone need 1,000 mm and the three cuts need another 9 mm. Use a longer prepared board or revise the part lengths if the design allows it. A different layout may require a different number of cuts.
Shop 101
Apply this reference to your project
Use your own project measurements and record how the result affects the material, setup or estimate.
- Name the material, dimension, or cost input that affects the decision.
- Use the reference and related calculator to check the measurement or estimate.
- Test or compare the result before committing final material, time, or client scope.
Try it with your own numbers
Common questions
What does kerf mean in woodworking?
Kerf is the width of material removed by a cutting tool, usually a saw blade. It is the gap left after the cut.
How do I calculate kerf allowance?
Multiply the blade kerf by the number of cuts that separate parts, then include any additional trim allowance required for milling and final sizing.
Is thin kerf always better?
A thinner kerf wastes less stock, but blade choice also depends on saw power, cut quality, stability, and the material. Use the blade appropriate to the job, then plan around its actual kerf.