Saw kerf explained: the slot your blade eats

Kerf means lost wood at each cut

Each pass of the blade eats a slot. On many table saws that slot runs near 1/8 inch. Thin trim blades eat less. Thick rip blades eat more. Read the tooth stamp or test in scrap to learn your true width.

The rule is plain. Each part needs its length plus one kerf, save the last part on the board. Four parts on one board need three kerf slots. At 1/8 inch each, that is 3/8 inch gone to dust. Skip that and your last part lands 3/8 inch short of the end.

1/8 inch example on a 96 inch board

Say you cut 24 inch parts from a true 96 inch board. Four parts need 96 inches of wood plus three kerf slots. That sum is 96 and 3/8. That is more than the board holds. So three parts fit with room to spare. The fourth needs a new board.

Type the same facts in the free cut planner with kerf at 0.125. You will see that split. Trim the rough ends first, then type the true length you can use. That keeps the plan true to your shop wood.

Leftover honesty: measure before the last cut

The shown spare already has all kerf cuts removed. But boards bend. Knots force shifts. Trim needs eat ends. So tape the board before your last cut. If the spare runs thin, cut the small parts first or pull a fresh board.

The plan uses a longest first fit. It fills one board, then starts the next. That gives a good shop plan fast. It is not a set best answer. Check each mark at the saw. This guide is shop math only, not build or safety advice. For photo size caps in plain words, see our JPEG KB limit guide.