Kerf — Woodworking Glossary

Kerf

Kerf is the slot — and the material removed from that slot — produced when a saw blade passes through wood. Every time a blade makes a cut, it does not simply divide the wood at a line; it destroys a thin strip of material equal in width to the blade's teeth. That lost material is the kerf.

The word comes from the Old English cyrf, meaning a cut or notch. In modern woodworking it refers specifically to the width of the cut, measured perpendicular to the blade's travel.

Why Kerf Matters for Cut Lists

Kerf is not a rounding error. On a single cut it is easy to ignore. Across a full layout of parts on a sheet of plywood, accumulated kerf can add up to an inch or more of lost material — enough to make a part come up short or force an unplanned seam.

Consider a sheet of 4'×8' plywood being ripped into 6" wide parts. Each rip cut removes roughly 1/8" of kerf. After 7 rip cuts, you have lost nearly 7/8" of usable width — almost enough to cost you an entire part. A cut list that does not account for kerf will tell you that 8 parts fit across a 48"-wide sheet (8 × 6" = 48"). In practice, after kerf, only 7 fit cleanly.

When building a cut list manually, you must subtract kerf from the available width between each successive part when planning your layout. This is one of the primary reasons woodworkers use cut list software: kerf accounting is handled automatically, so every layout reflects what is actually achievable on the saw.

Typical Kerf Widths by Tool

Different saws produce different kerf widths depending on blade thickness, tooth set, and tooth design.

Note that these are typical values. Actual kerf depends on the specific blade installed, its condition, and whether the blade has a tooth set (teeth alternately bent outward) or is a flat-grind design. Always measure your own blade's kerf if precision is critical — use a dial caliper to measure the slot width in a test cut.

Thin-Kerf vs. Full-Kerf Blades

Full-kerf blades are the industry standard at 1/8" (0.125"). They are robust, run true, and are the default choice for cabinet-grade table saws with powerful motors (3 HP and up).

Thin-kerf blades cut a narrower slot (typically 3/32" or about 0.094"). They waste less material per cut — an advantage on expensive hardwoods — and require less motor power to push through stock. They are popular on contractor saws and jobsite saws where motor power is limited.

The trade-off: thin-kerf blades are more prone to deflection (blade wander) under lateral load, which can affect rip cut accuracy on wide, dense stock without a proper featherboard or splitter.

For cut list planning purposes, the difference between 3/32" and 1/8" kerf is minor on most projects. For precision joinery or when maximizing yield from expensive lumber, knowing your exact kerf width matters.

Kerf and Crosscuts

Kerf affects rip cuts (along the grain) and crosscuts (across the grain) equally. When crosscutting multiple identical parts from a long board, each crosscut removes a kerf-width of length.

To calculate how many parts of length L fit on a board of length B with kerf K:

number of parts = floor((B + K) / (L + K))

The + K in the numerator accounts for the fact that the last part does not require a trailing cut. This formula assumes all cuts are made from a continuous board with no pre-existing defects to work around.

Kerf Bend Cuts

Kerf is also used intentionally in a woodworking technique called kerf bending (or kerfing). A series of closely spaced, shallow parallel cuts made partway through a board's thickness allows the remaining thin layer to flex, bending the wood around a curve. This technique is common in curved cabinet carcases, bent laminations, and decorative radius work.

In kerf bending, the kerf width and spacing are calculated deliberately to achieve a specific bend radius — the opposite of the typical goal of minimizing kerf impact.

How Cutly Handles Kerf

Cutly automatically applies your saw's kerf width to every layout calculation. When you set up a project, you specify your saw's kerf (default: 1/8"). The layout engine deducts kerf between every part as it packs pieces onto sheets and boards, so the cut count you see is always achievable in reality — not just on paper.

This means you never discover mid-cut that a part does not fit because accumulated kerf ate into your last board. The math is done before you touch the saw.

Related terms: Grain Direction, Rip Cut, Crosscut, Yield