Article
What Is Kerf? Blade & Bit Loss Explained
Cutlistor Team5 min read
Introduction
Every cut list optimizer asks for a kerf value, and almost every guide on this site mentions it in passing — but few explain what it actually is. Kerf is the width of material a blade or bit removes as it passes through your stock. It sounds trivial until you are forty cuts into a sheet and the yield does not match what you expected.
This guide defines kerf in plain terms, lists typical widths by tool so you are not guessing, shows how to measure your own saw or router, and works through a real example of how kerf changes sheet count on a cut list.
What kerf actually is
Kerf is the slot a cutting tool leaves behind — the material converted to sawdust, chips, or vapor as the blade, bit, or beam passes through. It is not the thickness of the saw blade's steel plate; it is the width of the cut it makes, which is usually slightly wider than the plate thanks to tooth set or carbide tips.
Kerf matters because a cut list optimizer needs to know how much space to remove between every part on a sheet or every segment on a stick. Ignore it, or underestimate it, and the optimizer will promise more parts per sheet or stick than you can actually cut.
Kerf also compounds. A single 3.2 mm miss on one cut is nothing. The same 3.2 mm lost on every one of forty cuts across a sheet run adds up to real material — sometimes enough to change how many sheets you need to buy.
Typical kerf by tool
Kerf varies by tool, blade or bit choice, and how sharp your tooling is. Use these as a starting point, then measure your own setup before committing to a full sheet run.
| Tool | Typical kerf | Notes |
|---|---|---|
| Thin-kerf table saw blade | 1.6-2.2 mm (~1/16 in) | Common on portable and hybrid saws to save power and material |
| Standard table saw blade | 2.8-3.2 mm (~1/8 in) | Most cabinet saws and panel saws ship with full-kerf blades |
| Circular saw / track saw | 2.0-2.8 mm | Varies by blade; track saws often run thinner-kerf blades |
| CNC router bit | 3.0-6.35 mm (1/8-1/4 in) | Kerf equals bit diameter, not a fixed constant - check your tool library |
| Panel saw / beam saw | 3.0-4.5 mm | Larger industrial blades typically run wider than a site table saw |
| Laser cutter | 0.1-0.3 mm | Thin kerf, but can widen on thicker material or an unfocused beam |
| Plasma / waterjet | 1.0-1.5 mm | Wider than laser; varies with nozzle size and material thickness |
| Hand saw | 1.0-1.5 mm | Rarely worth optimizing for, but relevant on fine joinery |
Ranges are general starting points. Always confirm against a test cut on your own machine before running a full job.
How to measure your actual kerf
Manufacturer specs and blade boxes give a starting number, but blade wear, tooth set, and bit runout change the real value. A five-minute test beats a guess.
- Mark two parallel lines exactly 100 mm (or 4 in) apart on a scrap piece.
- Cut along the outer edge of each line, keeping the blade or bit just touching the marked side.
- Measure the offcut strip left between the two cuts.
- Subtract the strip width from 100 mm (or 4 in) - the difference is your kerf.
- Repeat after a blade or bit change, and again if you switch materials that load the teeth differently.
Worked example: kerf changes your sheet count
Take a simple job: forty parts at 560 x 400 mm nested on 2440 x 1220 mm sheets. At 0 mm kerf — effectively ignoring it, which no optimizer should do by default — the parts appear to fit on fewer sheets than reality allows.
Set kerf to 3.2 mm, a typical full-kerf table saw blade, and every cut line now consumes an extra 3.2 mm of width or height. Across forty parts and dozens of cut lines, that adds up to enough lost material to push the layout from, say, six sheets to seven.
The gap between a 0 mm-kerf estimate and a 3.2 mm-kerf reality is exactly why a cut list calculator that ignores kerf always looks better on screen than it performs on the saw. Enter your measured kerf, not a guess, before you buy material.
Kerf mistakes that waste material
- Using a generic default (often 3 mm) without checking it against your actual blade or bit
- Forgetting to update kerf after swapping to a thin-kerf blade or a different router bit diameter
- Applying table saw kerf to a CNC job, or vice versa, on mixed workflows
- Ignoring kerf on linear cuts (lumber, trim, pipe) because it 'only matters for sheets' - stick length is lost the same way
- Re-using an old kerf value after tooth wear or a re-sharpening changes the cut width
How Cutlistor uses your kerf value
Both Cutlistor optimizers — sheet and linear — subtract your entered kerf from every cut line before nesting, not just from the outer edges of the stock. That means yield, sheet count, and stick count reflect what you will actually get on the saw or router, not a best-case estimate.
Set kerf once per job, or per material if you switch blades between panel types. Change it any time — the layout refreshes immediately, so you can compare a thin-kerf and full-kerf blade on the same cut list before deciding which to run.
Conclusion
Kerf is a small number with a compounding effect. Measure it instead of guessing, match it to the tool and blade or bit you are actually running, and keep it current when tooling changes. A cut list optimizer that takes kerf seriously will save you from ordering material you do not need — or worse, running short mid-job.