Woodworking Kerf Calculator

1. Enter how many pieces you are cutting.
2. Enter the finished length of each piece.
3. Enter your blade kerf; a typical table-saw blade is about 0.125 inch.
4. Read the stock length you need, including the kerf loss.

Kerf is the width of material a saw blade removes as it cuts, turned into sawdust. Every cut consumes a strip of wood as wide as the blade, so a series of cuts quietly eats into the length of your stock.

On a single cut the loss is tiny, but across many pieces it adds up. Ignoring kerf is a classic way to end up just short on the last piece, which is why careful woodworkers build it into their cut lists. It is one of those small details that separates a plan that works on the bench from one that only worked on paper, and it becomes more important the more pieces you are cutting from a single expensive board.

1. Multiply the number of pieces by their length for the wood in the pieces.
2. Multiply the number of cuts by the kerf width for the total loss.
3. Add the two for the stock length you need.
4. Divide the stock by 12 for feet if you prefer.

This treats one cut per piece, a safe assumption when parting pieces off a long board. Cutting from both ends or nesting can save a cut or two. For most bench work, though, planning one cut per piece is the safe default that guarantees you never run out of board partway through a run.

You need 10 pieces, each 12 inches long, cut with a 0.125 inch kerf blade. The pieces themselves are 120 inches of wood. Ten cuts at 0.125 inch lose 1.25 inches to kerf. So you need 121.25 inches of stock, just over 10 feet, not the 10 feet the pieces alone suggest. With a thicker 0.14 inch blade the loss grows to 1.4 inches. Multiply that across a big project of dozens of parts and the kerf alone can swallow the best part of a foot of timber, which is real money in figured hardwood and easily the difference between one board and needing two.

Blade Kerf

Thin-kerf blades remove less wood per cut than full-kerf ones, saving material over many cuts.

Number of Cuts

More pieces means more cuts, and the loss grows in step with them.

Cut Layout

Nesting parts and cutting from both ends of a board can remove a cut or two and its kerf.

Material

Hard, dense woods and abrasive sheet goods can call for wider blades, raising the kerf.

Typical blade kerfs and the loss over 20 cuts.

Band saws have the narrowest kerf, which is why they are favoured for resawing where every millimetre counts.

Buying Stock

Make sure a board is long enough to cut every piece with kerf included.

Cutting Many Parts

See how much material a batch of cuts really consumes.

Choosing a Blade

Compare how much a thin-kerf blade saves over a run of cuts.

1. Ignoring Kerf Entirely

Cutting a board to the exact sum of the pieces leaves you short on the last one.

2. Guessing the Kerf

Measure your blade or check its specification; kerfs vary more than people expect.

3. Forgetting the First Cut

Squaring one end of rough stock uses a cut and its kerf too.

4. Over-Counting Cuts

Nesting or cutting from both ends can remove a cut, so do not always assume the maximum.

The arithmetic is exact for the pieces, length and kerf you enter. It assumes a simple one-cut-per-piece layout on a long board.

Kerf is the width of material a saw blade removes on each cut, turned into sawdust. A typical table-saw blade has a kerf of about 0.125 inch.

Multiply the number of cuts by the kerf width. Ten cuts with a 0.125 inch kerf lose 1.25 inches of material.

Add the total kerf loss to the combined length of your pieces. Ten 12 inch pieces with a 1/8 inch kerf need 121.25 inches of stock.

Full-kerf table-saw blades are about 0.125 inch; thin-kerf blades around 0.091 inch. Band saws are far narrower, near 0.025 inch.

Yes. Over many cuts a thin-kerf blade removes noticeably less wood, which matters when material is expensive or short.

Barely. On one cut the loss is tiny, but across a batch of cuts it adds up and can leave you short.

Measure the width of a cut in scrap, or check the blade specification. It is usually printed on the blade.

Sometimes. Nesting parts and cutting from both ends of a board can save a cut and its kerf.

No. The calculator runs entirely in your browser and nothing you enter is stored or sent anywhere.

• Kerf (Wikipedia).
• Saw (Wikipedia).
• Circular saw blade (Wikipedia).