How do you measure a chainsaw bar and chain?

Measure a chainsaw bar and chain in four steps: bar length, pitch, gauge, and drive-link count. The bar's called length is the usable cutting length from where it exits the saw body to the tip, rounded to the nearest even inch, which is why a bar that measures 15.5 inches is sold as a 16-inch bar.

Pitch is the size of the chain, found by measuring the distance between any three consecutive rivets and dividing by two. Common results are 1/4, .325, 3/8 low profile, 3/8 standard, and .404 inch. On most saws the pitch is also stamped on the bar or on a drive link, so you can read it rather than measure it.

Gauge is the thickness of the drive link, the part that rides in the bar groove, and it must match the bar exactly. The four common gauges are .043, .050, .058, and .063 inch, and the bar is nearly always stamped with its gauge. Drive-link count is simply the number of drive links in the loop, which you count all the way around the chain; this sets the true length for a given bar.

Why divide the rivet spacing by two for pitch?

Pitch is defined as half the distance between three consecutive rivets because the rivets are not evenly spaced along the chain, so measuring across three rivets and halving it gives a true, repeatable figure. Measuring between just two rivets would give inconsistent numbers depending on which pair you picked. Because the result is a standard value, you can round your measurement to the nearest listed pitch: a reading near 0.375 inch is 3/8, and one near 0.325 inch is .325. If your measurement falls between two, re-measure carefully or read the stamp, because pitch is one of the two numbers that absolutely must match the sprocket.

How do you measure the called bar length?

Measure the called bar length from the front face of the saw body, where the bar emerges, to the very tip of the nose, then round to the nearest even inch. This called or cutting length is always a little shorter than the whole bar, part of which is buried inside the saw under the cover. The full physical length of the bar does not matter for buying; the called length is what saws and bars are sold by. If you need the mounting details for a replacement bar rather than a chain, you also need the mount pattern and oil-hole layout, which our chainsaw bars guide covers.

What if the bar stamp is worn off?

If the bar stamp is worn smooth, measure the chain directly instead of reading it. Lay the old chain flat, measure across three rivets and halve it for pitch, and use a caliper or feeler gauges on a drive link for gauge — or take a drive link to a dealer who can match it. The drive-link count is the one figure you must physically count regardless, so run your finger around the loop and count every tab, marking your starting point so you do not lose your place. A worn stamp is common on a well-used saw, and measuring the chain is a reliable fallback.

A worked example

Say you have an unlabeled 18-inch bar and an old chain to match. You measure across three rivets and get about 0.65 inch, which halves to .325-inch pitch. A caliper on a drive link reads 1.5 mm, which is .058-inch gauge. Counting around the loop gives 72 drive links. Those three numbers — .325 pitch, .058 gauge, 72 drive links — are the exact specification to order, and the 18-inch figure is only a rough cross-check. If you want a second check, look up the bar's model number in the maker's chart and confirm it lists the same drive-link count; when the measured count and the chart disagree, trust the physical count on the chain you are replacing, because bars of the same nominal length are made in more than one drive-link version. Combine those chain numbers to order an exact replacement, and use the bar length and stamp to match a new bar. Our chainsaw bars guide and full chainsaw chains guide walk through matching bar and chain so the two always agree.