Kerf is the width of material removed by a cutting tool — the slot left behind after the blade, bit, or abrasive passes through. It equals the blade plate thickness plus the set of the teeth (how far they protrude sideways).

How do I find my blade's kerf width?

Check the blade packaging or manufacturer spec sheet. A standard 10-in table-saw blade is commonly 1/8 in (3.175 mm) full-kerf or 3/32 in (2.38 mm) thin-kerf. You can also measure the slot left in a scrap piece with calipers.

Does every cut add the full kerf loss?

Yes — each cut through a board removes one full kerf width from the remaining material. If you make 3 cross-cuts from a single board, the board loses 3× the kerf width total.

Why do my results look slightly different from manual calculation?

This tool works in decimal inches internally. Fractional-inch entries (e.g. 1/8) are converted to their exact decimal equivalent, so results are mathematically exact to floating-point precision.

Can I use this for CNC routing?

Yes. Enter the router bit diameter as the kerf width. For inside pockets you may also need a separate offset calculation, but kerf loss along a straight cut is the same principle.

Kerf Allowance Calculator

Name: Kerf Allowance Calculator
Availability: InStock
Author: Nham Vu

Enter your blade kerf width and the number of cuts to find how much material is lost, and adjust your cut list so final pieces match intended measurements.

Cut Parameters

Units

Blade Kerf Width (inches)

Standard full-kerf table saw blade: 1/8 in (3.175 mm)

Number of Cuts

Cuts that cross the dimension you are calculating.

Total Stock Length (inches)

Length of the board or sheet before any cuts (optional).

Intended Finished Piece Length (inches)

Fill in the parameters and press Calculate.

Total Kerf Loss

—

inches

Adjusted Cut Length

—

per piece

Adjusted Cut List

Cut #	Mark at stock	Finished piece

Tip: Measure your actual kerf with calipers on scrap — spec-sheet values can differ by 0.01–0.02 in from the real cut. For critical fits, sneak up on the final dimension with a test cut first.

Summary

Enter your blade kerf width and the number of cuts to find how much material is lost, and adjust your cut list so final pieces match intended measurements.

How it works

Enter the blade kerf width (check your blade spec sheet; typical table-saw kerf is 1/8 in or 3.175 mm).
Enter the number of cuts that will cross the dimension you care about.
Enter the intended finished length of each piece.
The calculator multiplies kerf × cuts to find total material lost, then divides that loss across your pieces to give adjusted cut lengths.
Switch between inches (fractional or decimal) and millimeters using the unit toggle.

Use cases

Ripping a sheet of plywood into cabinet panels where every kerf shifts the remaining width.
Cross-cutting lumber into multiple identical parts that must all hit a precise length.
Metalworking: accounting for band-saw or angle-grinder kerf when cutting bar stock.
CNC routing: adjusting toolpath offsets when the end-mill diameter removes material.
Tile cutting: factoring in diamond-blade kerf before scribing a row of tiles.

Frequently Asked Questions

Last updated: 2026-06-13 · Reviewed by Nham Vu