Chainsaw bar gauge is the thickness of the drive links that ride inside the guide bar groove, measured in inches. There are four in common use: .043" (1.1mm), .050" (1.3mm), .058" (1.5mm) and .063" (1.6mm). Your chain's gauge must match your bar's groove exactly β a chain that's too thick won't seat in the groove at all, and one that's too thin will lean under load, cut in a curve and wear out your bar rails.
Gauge is one of three numbers that identify a chainsaw chain, alongside pitch and drive-link count. It's also the one people get wrong most often, because two chains with identical pitch and identical drive links can still be completely incompatible if the gauge differs β and they look nearly identical side by side.
What Gauge Actually Measures
Turn a chain over. The shark-fin shaped tangs pointing down are the drive links β they sit inside the groove machined into your guide bar and take the drive from the sprocket.
Gauge is simply how thick those tangs are. The bar groove is machined to a matching width, so the chain rides in a track that holds it upright and square to the timber. Get that relationship right and the chain cuts straight. Get it wrong and everything downstream suffers.
The Four Gauges
| Gauge | Metric | Typically found on |
|---|---|---|
| .043" | 1.1mm | Narrow-kerf battery saws, small Stihl (MS 170β182), Makita LXT/XGT, pole pruners |
| .050" | 1.3mm | The most widely used gauge worldwide β mid-size consumer saws, Stihl MS 211, Echo CS-310 |
| .058" | 1.5mm | Many Husqvarna and Echo models, including the 435β455 range and 562/572 XP |
| .063" | 1.6mm | Heavier-duty applications β professional Stihl saws, and most Australian .325" Stihls |
An important caveat: gauge is set by the individual saw model, not by brand or country. Stihl uses .043" on the MS 170, .050" on the MS 211 and .063" on the MS 250 β three gauges across one manufacturer's small-saw range. Don't assume from the badge on the cover.
What Goes Wrong When the Gauge Doesn't Match
Too thick for the groove
Straightforward: the chain won't seat. A .050" chain simply will not enter a .043" bar groove. You'll know immediately, which is the safer of the two failures.
Too thin for the groove
This is the dangerous one, because it appears to work. A .043" chain fitted to a .050" bar drops into the groove and tensions up looking fine. Under cutting load it leans sideways in the oversized track, and three things follow:
- The cut curves. The chain isn't held square, so it wanders off line.
- The bar rails wear unevenly. A leaning chain grinds one rail lower than the other, which eventually ruins the bar even after you fit the correct chain.
- Control suffers. A chain that can move laterally in the groove is less predictable in the cut.
(If your saw is already cutting crooked, our crooked cut diagnostic guide walks through the causes, gauge mismatch included.)
The .043" Misconception
Narrow-kerf .043" chain is sometimes dismissed as flimsy. It isn't β it's engineered thin on purpose.
A thinner chain cuts a narrower kerf, removing less wood per pass. Less material removed means less friction and less power required, which is exactly what a 35cc homeowner saw or a battery motor needs. Fitting a heavier chain to one of those saws wouldn't make it stronger; it would bog the engine and flatten the battery faster.
Run the gauge your bar is machined for. (More on this in our narrow kerf guide for battery saws.)
How to Find Your Gauge
- Read the bar stamp. Most guide bars carry the gauge stamped on the flat near the mounting slot, shown either in inches (.050") or millimetres (1.3mm).
- Check the old chain's packaging if you still have it.
- Look it up by model. Search by Chainsaw returns the full specification for your saw.
- Ask us. Send a photo of your bar through the chat and we'll confirm it before anything ships β that's our Guaranteed Fit promise.
Measuring a drive link with calipers is possible but rarely reliable β the tangs wear, and a worn .050" link can measure closer to .045". Trust the bar stamp over the tape.
Chainsaw Bar Gauge β FAQ
What is chainsaw bar gauge?
It's the thickness of the chain's drive links, which must match the width of the groove machined into your guide bar. The four common gauges are .043", .050", .058" and .063".
What are the standard chainsaw chain gauges?
.043" (1.1mm), .050" (1.3mm), .058" (1.5mm) and .063" (1.6mm). The .050" gauge is the most widely used worldwide.
What happens if the chain gauge is too thin for the bar?
The chain fits and tensions normally, but leans sideways in the oversized groove under load. That causes crooked cuts, uneven bar rail wear and reduced control β which is why it's the more dangerous of the two mismatches.
What happens if the chain gauge is too thick?
It won't seat in the bar groove at all. You'll find out immediately, which makes it the safer error.
Is gauge the same as pitch?
No. Gauge is the thickness of the drive links; pitch is the distance between rivets divided by two. Both must match your saw, along with the drive-link count.
How do I find my chainsaw's gauge?
Read the stamp on the guide bar near the mounting slot β it's usually shown as .050" or 1.3mm. If it's worn off, look the saw up by model rather than trying to measure a worn drive link.
Can I use a different gauge chain on my bar?
No. The bar groove is machined to a specific width, so only a matching gauge will run correctly. Changing gauge means changing the bar.
Is .043" gauge chain weaker than .050"?
It's thinner by design rather than weaker in application. Narrow-kerf .043" removes less wood per pass, reducing friction and power draw, which suits small petrol and battery saws that have no power to spare.
Know your gauge? Find your chain
Enter the numbers off your bar, or search by saw model. Every chain is checked against your bar stamp before it ships β our Guaranteed Fit promise.