Match your chainsaw file to your chain pitch and gauge
A chainsaw file is a round metal tool that sharpens the teeth on your chain. The file size you need depends on two measurements of your chain: the pitch (distance between rivets) and the gauge (thickness of the drive links). Using the wrong file size will either skip over teeth without sharpening them or remove too much metal and weaken the tooth.
The pitch of your chain is the most important number. It determines the file diameter — the width of the round file itself. Gauge determines how deep you file into each tooth. Most chainsaws use one of four common pitches: .325 inch, .375 inch (also called 3/8), .404 inch, or .063 inch. You can find your chain's pitch stamped on the side of the bar or printed in your owner's manual.
Key Takeaways
- Chain pitch is the distance between rivets on your chain and determines which file diameter you need — .325 pitch uses a 5/32-inch file, while .375 and .404 pitches use a 7/32-inch file.
- Gauge (the thickness of drive links) determines how deep the file cuts into each tooth and ranges from .043 to .063 inch, affecting file depth but not diameter.
- You can find your chain's pitch and gauge on the side of the bar, on the chain itself, or in your owner's manual — do not guess, because using the wrong file size dulls your chain faster.
- A file holder or guide keeps the file at the correct angle and depth, which is more important than the file itself for getting a sharp, even edge.
- Round files wear out and should be replaced when they no longer cut smoothly or when you have filed all four sides of the file.
Common chainsaw file sizes by pitch
The chart below shows the standard file diameter for each chain pitch. These are the sizes you will find at hardware stores and online retailers.
| Chain Pitch | File Diameter | Common Chainsaw Models |
|---|---|---|
| .325 inch | 5/32 inch (4.0 mm) | Stihl MS170, MS180, Echo CS-310, Husqvarna 435 |
| .375 inch (3/8) | 7/32 inch (5.5 mm) | Stihl MS250, MS290, Echo CS-400, Husqvarna 455 |
| .404 inch | 7/32 inch (5.5 mm) | Stihl MS660, Husqvarna 390, older large saws |
| .063 inch | 13/64 inch (5.2 mm) | Larger professional saws, less common in consumer models |
If you own a mid-size homeowner saw (Stihl MS250, Echo CS-400, Husqvarna 455), you almost certainly have a .375-inch pitch chain and need a 7/32-inch file. Small saws often use .325 pitch and a 5/32-inch file. Large professional saws use .404 or .063 pitch.
How to find your chain pitch and gauge
The easiest way is to look at the side of your chainsaw bar. Most manufacturers stamp the pitch and gauge directly into the metal. You will see something like ".375 .063" or ".325 .050" — the first number is pitch, the second is gauge.
If the bar is worn or the stamp is not visible, check your owner's manual. The manual lists the original chain specifications and often includes a diagram showing where to look on the bar itself. You can also count the rivets on your chain: measure the distance from the center of one rivet to the center of the third rivet ahead, then divide by two. That gives you the pitch.
Gauge is harder to measure without calipers, so if you cannot find it stamped anywhere, bring the chain to a hardware store or saw shop and ask them to measure it. Gauge ranges from .043 to .063 inch, and using the wrong gauge will not sharpen your chain evenly.
Why gauge matters for filing depth
The gauge of your chain determines the depth setting — how far the file cuts into each tooth. Thicker gauge chains (.063 inch) need a deeper file cut than thinner ones (.043 inch). If you file too shallow on a thick-gauge chain, the teeth will not cut. If you file too deep on a thin-gauge chain, you will weaken the tooth and it will break.
Most file holders or guides have a depth gauge built in, which sits on top of the tooth and stops the file at the right depth. If you are filing by hand without a guide, you need to know your gauge so you can estimate the correct depth. A good rule is to file until you see a small curl of metal come off the tooth — that means you are cutting.
File holders and guides make a bigger difference than file size
The file itself is only half the tool. A file holder or guide clamps around the file and sits on your chain, keeping the file at the correct angle (usually 25 to 35 degrees) and preventing you from filing too deep or too shallow. A guide costs $15 to $40 and will produce a sharper, more even edge than hand-filing alone.
Popular brands include Stihl's round-file holder, Oregon's file guide, and Husqvarna's filing kit. Most guides are universal and work with any round file diameter, so you only need to buy one. The guide sits on the tooth and the file slides through a slot at a fixed angle. You push the file forward and lift it back without cutting on the return stroke.
If you do not have a guide, you can still file by hand, but you need a steady hand and experience. Mark the correct depth on the file with a marker or tape so you can see when you have filed deep enough. File at a consistent angle — most teeth are filed at 25 to 35 degrees to the bar, though some saw designs use different angles.
When to replace your file
Round files wear out. The cutting edges become dull and the file stops removing metal from the tooth. A dull file will heat up the tooth and can actually harden the steel, making it harder to sharpen next time.
Most files have four usable sides. You can rotate the file a quarter turn after each tooth or after each pass around the chain, so one file lasts through four complete sharpenings. After that, the file is too worn and should be replaced. If the file is still sharp but you have used all four sides, you can continue using it, but it will wear faster.
A new file costs $5 to $15 depending on the diameter and brand. Replacing a worn file is cheaper than buying a new chain or paying a shop to sharpen for you.
Frequently Asked Questions
Can I use a 7/32-inch file on a .325-inch pitch chain?
No. A 7/32-inch file is too large and will not fit properly in the tooth gullet. It will either skip over teeth or sit too high and not sharpen them. Always use the file size that matches your chain pitch.
What if I cannot find my chain pitch anywhere?
Take the chain to a hardware store, saw shop, or dealer and ask them to identify it. They can measure the pitch in seconds. You can also post a clear photo of the chain online in a chainsaw forum and someone will identify it for you.
Do I need to file every tooth the same number of times?
Yes. Each tooth should receive the same number of file strokes so they all end up the same length and sharpness. If one tooth is shorter or duller than the others, the chain will pull to one side when you cut.
Is a battery-powered file sharpener better than hand-filing?
Battery sharpeners are faster and more consistent, but they cost $100 to $300 and require you to set the angle correctly. Hand-filing with a guide is slower but gives you more control and works just as well if you have the right file size and a steady hand.
How often should I sharpen my chain?
Sharpen when the chain stops cutting straight or when you have to push hard to make it cut. For regular use, that is usually every few hours of cutting. A dull chain is dangerous because it can kick back or bind, so do not wait until the chain is very dull.