How to measure a chainsaw chain
To measure a chainsaw chain you do not need the model number: any one of these four things identifies it. The model plate on the saw, the number stamped on the chain, the drive link count (that is the chain length), or the bar length. Measure your chain or your bar first, then read the number off it.
The model plate on the saw
Look for a plate or a sticker on the saw body that carries a brand and a model, for example Stihl MS170 or Husqvarna 455. Type it in the picker and the page gives you the pitch, gauge, drive links and the chain code to buy.
The number stamped on the chain
Oregon stamps a number on the drive links. That number identifies the chain type, and the type gives you the pitch and the gauge. Find it here:
See all stamp numbers
| Stamp | Pitch | Gauge |
|---|---|---|
| 11 | 3/4" | .122" |
| 16 | .404" | .063" |
| 18 | .404" | .080" |
| 20 | .325" | .050" |
| 21 | .325" | .058" |
| 22 | .325" | .063" |
| 25 | 1/4" | .050" |
| 26 | .404" | .058" |
| 27 | .404" | .063" |
| 33 | .325" | .050" |
| 34 | .325" | .058" |
| 35 | .325" | .063" |
| 50 | .404" | .050" |
| 51 | .404" | .058" |
| 52 | .404" | .063" |
| 58 | .404" | .058" |
| 59 | .404" | .063" |
| 68 | .404" | .063" |
| 72 | 3/8" | .050" |
| 73 | 3/8" | .058" |
| 75 | 3/8" | .063" |
| 80 | .325" LP | .043" |
| 90 | 3/8" LP | .043" |
| 91 | 3/8" LP | .050" |
| 95 | .325" | .050" |
How to measure the chain length in drive links
Lay the old chain flat. The drive links are the tabs underneath that ride in the bar groove. Mark one with a paint pen and count until you are back at the marked link. That count is the chain's length.
Wear does not add or remove drive links, so a worn chain counts the same. If your number looks wrong, count again from a marked link before you doubt it.
How to measure the bar (guide bar) length
Measure from the front of the saw body to the tip of the bar, then round up to the nearest even inch. That is the called length, not the full length of the steel. The drive link count for that length depends on the pitch, so one length has several right answers.
Fitting the chain: tension and direction
- 1Turn the engine off and wear protective gloves.
- 2Loosen the guide bar mounting nuts on the side of the saw.
- 3Insert a screwdriver or a scrench in the tensioning slot of the bar.
- 4Move the guide bar forward, away from the saw, as far as it goes.
- 5Tighten the back mounting nut first, then the front nut.
The chain should feel snug but still pull freely by hand. Wrong tension causes more chain and bar problems than anything else, so check it often.
On a sprocket nose bar, do the snap test: grasp the chain along the bottom of the bar, pull down and let go. It should snap back and sit solidly against the bar.
The sprocket wears out with the chain
The pitch has to match the drive sprocket you already have, and a worn sprocket will damage a new chain. Never run a new chain on a worn sprocket, and replace the drive sprocket every two chains, or sooner.
The count on the page is not the count on my chain
Your bar may be a different length.
Each count on a saw's page is for one bar length. A longer or shorter bar takes a different count, and the count changes with the pitch too.
Count again from a marked link.
Most miscounts come from losing the start: mark one link and finish on the same one.
Pitch and gauge still have to match.
A chain with the right link count but the wrong pitch or gauge will not run, however close the number looks.