Match the pitch and gauge to your bar, not the bar length.

The short answer: there’s no single “right” pitch and gauge for a given bar length — it depends on what the saw is designed for. But you can measure them in about two minutes.

Pitch is the distance between drive links, measured from the center of one rivet to the center of the next, then divided by two. (Or just measure over three rivets and divide by two — same result.) Common pitches are 1/4", 3/8", .325", and .404". A smaller pitch usually means a smoother cut but slower chain speed.

Gauge is the thickness of the drive links that ride in the bar groove. It’s typically .043", .050", .058", or .063". You measure it with a caliper or a gauge tool — not a guess.

Here’s the real-world rule: If you have a consumer saw with a 16"–20" bar, it’s probably 3/8" pitch and .050" gauge. Go bigger (like 24"+ for a pro saw) and you might step up to .325" or .404" pitch with a thicker gauge. But always check what the saw’s manual says. The bar itself will have the pitch and gauge stamped near the mount — look for numbers like “3/8 .050” or “72DL” (drive links).

Don’t trust “this bar length uses that chain size.” I’ve seen 18" bars with 3/8" pitch and .050" gauge, and 18" bars with .325" pitch and .058" gauge. Measure twice, buy once.