Chainsaw Bar and Chain Size Guide: Pitch, Gauge, and Length Explained

"16-inch chain" isn't actually enough information to buy a replacement chain that fits — bar length only tells you roughly how long the chain is, not whether it will physically engage your bar and drive sprocket. Two 16-inch saws from different brands can need completely different chains.

The good news is that correctly sizing a chain only takes three numbers plus a count: pitch, gauge, drive link count, and bar length. All three specs are usually stamped on the bar itself or printed in the owner's manual, so you rarely have to guess.

Why bar length alone doesn't determine chain fit

Bar length describes the cutting length of the guide bar, not the full spec of the chain that rides on it. Two saws with the same bar length can use different chain pitch or gauge depending on the saw's drive sprocket and the groove width machined into the bar.

That's why chain packaging always lists pitch and gauge alongside length — buying by length alone is the most common reason homeowners end up with a chain that doesn't fit their saw.

Bar length: how to measure it correctly

Measure from the tip of the bar to where it disappears into the saw's body (the felling mark or bar cover), not the bar's true overall length — the last inch or two sits inside the saw and isn't cutting length. Most manufacturers round this measurement to the nearest even number, which is the size printed in the saw's specs (14-inch, 16-inch, 18-inch, and so on).

If you no longer have the manual, this cutting-length measurement is usually stamped directly on the bar near the mounting slot, along with the pitch and gauge.

Pitch: the chain-to-sprocket spacing

Pitch is the distance between any three consecutive rivets on the chain, divided by two, and it has to match your saw's drive sprocket exactly. The common sizes on homeowner saws are 1/4 inch, .325 inch, 3/8 inch, and .404 inch, with 3/8-inch and .325-inch pitch covering most residential gas and battery saws.

A chain with the wrong pitch simply won't seat correctly on the sprocket or in the bar's guide groove, so this isn't a spec you can round or approximate.

Gauge: matching the drive link to your bar's groove

Gauge is the thickness of the chain's drive links, measured in thousandths of an inch, and it has to match the width of the groove cut into your bar. Common gauges are .043, .050, .058, and .063 inch — a chain with too thin a gauge will feel loose and rattle in the bar groove, while too thick a gauge won't seat at all.

Gauge is easy to confuse with pitch since both are small decimal numbers on the box — pitch is spacing along the chain, gauge is drive link thickness, and a replacement chain needs both to match, not just one.

Drive link count: why two chains of the same length can differ

Drive link count is the number of individual drive links in the loop, and it's the spec that actually guarantees a correct fit for a given bar — two chains with identical pitch and gauge can still fail to fit if the drive link count is different, since it determines the chain's total loop length.

If you're ordering a chain without the bar in front of you, drive link count (sometimes listed as "DL") is the most reliable number to match, especially after the original bar or chain has been replaced at some point and no longer matches factory specs exactly.

Putting it together when you order a replacement chain

A typical replacement chain listing reads something like "18 inch, .325 pitch, .050 gauge, 72 drive links" — all four numbers need to match your saw, not just the bar length. If you're unsure of any of them, the most reliable method is reading the stamp on the bar itself rather than guessing from the saw's model name.

When in doubt, bring the old chain (or a photo of the bar's stamped specs) to a hardware store or saw shop — matching a physical sample avoids the guesswork of cross-referencing part numbers across brands.