There is nothing more frustrating than a blunt chainsaw. Instead of slicing through logs like butter, it burns, smokes, and rattles your arms. While we stock a huge range of replacement Chainsaw Chains at CompassGM, you can often extend the life of your current chain significantly simply by sharpening it.
However, using the wrong size file is worse than not sharpening at all. A file that is too small will create a weak, hooked edge that snaps instantly. A file that is too large will strip the cutting edge away completely, ruining the chain.
The correct file size is determined entirely by the Pitch of your chain. This guide will help you identify your chain type and select the perfect file for your Stihl or Echo chainsaw.
The Quick Answer: File Size Chart
If you already know your chain’s “Pitch,” use this table to find your file.
| Chain Pitch | File Diameter (mm) | File Diameter (Imperial) | Typical Usage |
| 1/4″ | 4.0mm | 5/32″ | Small pruning saws & carvers |
| 3/8″ LP (Low Profile) | 4.0mm | 5/32″ | Most common home garden saws (Stiga/Mountfield electric & small petrol) |
| .325″ | 4.8mm | 3/16″ | Mid-range farm & estate saws |
| 3/8″ Standard | 5.2mm or 5.5mm | 13/64″ or 7/32″ | Large professional forestry felling saws |
| .404″ | 5.5mm | 7/32″ | Heavy-duty professional saws |
How to Find Your Chain Pitch
If you don’t know your pitch, don’t guess. Here are three ways to find it.
1. Check the Guide Bar
The easiest method is to look at the “tail” of the guide bar (the end that sits inside the chainsaw casing). Manufacturers like STIHL and ECHO almost always stamp the technical specs here. Look for a fraction or decimal like 3/8″ P or .325″.
2. Check the Chain ID Code
Look closely at the “Drive Link” (the shark-fin-shaped tooth that sits inside the bar groove).
Stihl Chains: Stihl uses a specific digit stamped on the cutter to indicate pitch. A ‘6’ typically indicates 3/8″ Picco (requires 4.0mm), while a ‘2’ often indicates .325″ (requires 4.8mm).
Oregon Chains (often on Echo): If you see 91, it is a 3/8″ Low Profile chain (needs a 4.0mm file). If you see 20, 21, or 22, it is a .325″ chain (needs a 4.8mm file).
3. The “3 Rivet” Rule (Measure It)
If all markings have worn off, you can measure it.
Take a tape measure.
Measure the distance between any three rivets (the round studs holding the links together).
Divide that number by 2.
Example: If the distance between three rivets is 0.65 inch (approx 16.5mm), your pitch is .325 inch.
Brand-Specific Advice
Stihl Chainsaws
Stihl uses its own terminology which can be confusing.
Picco (or ‘P’): If you see “3/8 P” or “Picco” on your bar, this is the same as “Low Profile.” It is standard on homeowner saws like the MS 170, MS 180, and MS 230.
You need: A 4.0mm (5/32″) file.
Rapid: If you have a larger farm saw (like an MS 271 or MS 291), it likely runs .325″ chain.
You need: A 4.8mm (3/16″) file.
Echo Chainsaws
Echo saws generally follow standard industry sizing, often using Oregon chains out of the box.
Top Handle & Small Rear Handle (e.g., CS-2511T, CS-310): Typically use 3/8″ Low Profile.
You need: A 4.0mm (5/32″) file.
Mid-Range (e.g., CS-420, CS-4510): Often run .325″ chain.
You need: A 4.8mm (3/16″) file.
Round vs. Flat Files: You Need Both
To sharpen a chain properly, you actually need two files.
The Round File: This sharpens the semi-circular cutting tooth (the part that cuts the wood).
The Flat File: This is used to lower the “Depth Gauge” (the small metal fin in front of the cutter). If this fin is too high, the cutter cannot reach the wood, and you will just create dust. If it is too low, the saw will be aggressive and grabby. Use a flat file with a depth gauge tool to keep this at the correct height.
Conclusion
Sharpening is a skill that takes patience, but having the right file makes it infinitely easier.
Small garden saw (Stihl MS170 / Echo CS-310)? Grab a 4.0mm file.
Mid-sized farm saw? Grab a 4.8mm file.
Big pro logger? Grab a 5.5mm file.
If you are still unsure, simply bring your old chain (or the whole saw) into our trade counter.
