Every saw cut turns a strip of your material into sawdust. That strip is the kerf, and on a long cut list it is the difference between a plan that works and one that comes up a piece short. Here is what kerf is, how wide it usually is, and how to build it into a cut list.
Kerf is the width of the slot a blade leaves behind. It is at least as wide as the blade's teeth, which are set slightly wider than the blade plate. A cut that is marked at 16 inches and made on the wrong side of the line produces a piece that is a blade-width shorter than you wanted, and the piece next to it picks up the difference.
Do not rely on a table. The most reliable number is your own: make a cut in scrap, measure the slot, and use that value.
You lose one kerf for every cut that separates two pieces, not one per piece. Cutting a board into n pieces takes n − 1 cuts when the last piece is what remains of the board. On a sheet, each straight cut across the sheet loses a kerf. Edges that are already on the sheet's border need no cut, so a piece that spans the whole width of a sheet owes no kerf in that direction.
Boards. You need six pieces at 16" and have 8-foot (96") boards. Six times 16 is exactly 96, so with a blade that removes nothing, one board is enough. With a 1/8" kerf the six pieces need 96.625", which does not fit, so the plan needs 2 boards.
Sheets. You need eight strips of 48" x 12" from a 4x8 foot (48" x 96") sheet. With no kerf, they fill exactly one sheet: eight 12-inch strips make 96 inches. With a 1/8" blade, each cut costs a little length, only seven strips fit, and the plan needs 2 sheets. The numbers here come from our calculators, run with kerf set to 0 and to 0.125.
When a plan fits "exactly", suspect kerf. If your cut list adds up to the full length of a board or sheet, it almost never works in practice. Check the plan with your real blade width.
Try it: set the blade width in the length cutting calculator or the sheet cutting calculator and see how the plan changes.
Kerf is the width of material a saw blade removes when it cuts. It is the thickness of the slot left in the board or sheet, and it is at least as wide as the blade's teeth.
A full-kerf table saw or miter saw blade removes about 1/8 inch. A thin-kerf blade is often about 3/32 inch. Measure your own blade with a test cut to be sure.
You count one kerf for every cut that separates two pieces. Cutting a board into n pieces takes n minus 1 cuts. Edges that fall on the border of the board or sheet need no cut.
Yes, whenever a plan fills a board or sheet almost exactly. Six 16 inch pieces from an 8 foot board need two boards once a 1/8 inch kerf is counted.
