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How to verify your chain size

Three checks, in order of reliability. Do the first one that your bar allows — together they take about five minutes and they settle arguments that model charts (including ours) cannot, because they describe the bar actually fitted to your saw.

Method 1 — Read the bar tail stamp

  1. Switch the saw off, let it cool, and wear gloves — a dull chain still cuts skin.
  2. Remove the clutch cover (usually two nuts on the side of the saw) and lift the bar and chain off together.
  3. Find the stamped text on the flat of the bar near the tail (the mount end). Clean off oil and sawdust with a rag; a phone flashlight at an angle makes faint stamps readable.
  4. Read off, in order: bar length, pitch, gauge, and — on most bars — the drive-link count for the correct loop.

Worked examples from real bars:

  • 18″ · .325 · 050 · 72 on a Husqvarna 450 Rancher bar → .325″ pitch, .050″ gauge, 72 drive links (Husqvarna H30 / X-CUT SP33G, Oregon 95TXL).
  • A Forestry Forum member's bar stamp read …058-1.5 … 325 72 DL → .325″ pitch, .058″ gauge (1.5 mm), 72 drive links. Note the gauge shown both ways — inches and millimetres.
18″ .325 .050 72 DL Stamp sits on the flat, near the tail Mount slot & oil hole Metric twins: .050″ = 1.3 mm, .058″ = 1.5 mm, .063″ = 1.6 mm
Where the stamp lives, and how the same gauge appears in millimetres on many bars.

Method 2 — Count the drive links

If the stamp is worn away, your old chain still knows the answer — as long as it was the right chain. Mark one drive link (the tangs on the underside of the loop) with chalk, then count all the way around and stop when you reach the mark again. Full instructions with a diagram are on the identification chart. If the old chain was wrong (it happens — it is the most common reason people land on this site), use Method 3 for pitch and gauge and match the count to your bar length in the model charts.

Method 3 — Measure pitch and gauge

Pitch

  1. Measure the distance between the centres of any three consecutive rivets on the chain.
  2. Divide by two. That is the pitch.
  3. Results you will actually see: ≈ 0.650″ → .325″ pitch (3 rivets span 0.650″), 0.750″ → 3/8″, 0.808″ → .404″. A 3/8″ low-profile chain also spans 0.750″ — it is told apart by its smaller, lower cutters and is what small saws use.

Gauge

  1. Gauge is the thickness of a drive link's tang — the part that rides in the bar groove.
  2. Measure it with a caliper if you have one: .043″ / .050″ / .058″ / .063″ (1.1 / 1.3 / 1.5 / 1.6 mm).
  3. No caliper? The bar stamp (Method 1) states the gauge the bar was made for, and that is the number that matters — the chain must match the bar groove, not the other way round.
When the stamp and the chart disagree

Believe the stamp and the count. Bars get swapped, saws get sold with non-standard setups, and manufacturers change factory fitments mid-model-run — shopping results for the Stihl MS 250 note a gauge change on later production. Our model pages show the factory combinations we could verify and flag every disagreement we found instead of quietly picking one.

Safety, briefly and seriously

A chain that is wrong for the bar — wrong gauge, wrong pitch, wrong length forced onto the sprocket — can derail at speed. Never run a chain that does not sit fully in the bar groove, never “make do” with a near-enough loop, and always follow the saw manufacturer's manual for fitting, tensioning and protective equipment. If you are unsure, a dealer will check a bar and chain over the counter in minutes. See our Terms of Use for the full disclaimer.