You can replace a chainsaw chain yourself in about 15 minutes with just two tools

A chainsaw chain dulls or breaks during normal use, and replacement is straightforward enough that you do not need a mechanic. You will need an adjustable wrench (or the wrench that came with your saw) and a new chain that matches your saw's bar length and pitch. The whole job takes longer to read about than to do.

The steps are the same whether your saw uses a side-access cover or a top-mounted sprocket, though the exact bolt locations differ slightly by model. Check your owner's manual for your specific saw's bar length and chain pitch before you buy a replacement — these numbers are printed on the bar itself or in the manual, and buying the wrong size means a wasted trip back to the store.

Key Takeaways

  • You need the correct bar length and chain pitch for your saw; these are printed on the bar or in your manual, and a wrong size will not fit.
  • Loosen the side cover bolts or top bolts (depending on your model) until the bar moves freely, then slip the old chain off and the new one on.
  • Tension the new chain so it sits snug against the bar but still slides by hand — too loose and it falls off, too tight and it burns out the motor.
  • The entire replacement takes 10 to 15 minutes and requires only a wrench and the new chain.

Step 1: Unplug the saw and let it cool

Turn off the saw and unplug it if it is electric, or let a gas saw sit for at least five minutes after you shut it off. The chain and bar get hot during use, and touching them while warm can cause a burn. A cool saw is also safer to work on because there is no risk of accidental startup.

While the saw cools, locate the bolts that hold the side cover or top cover in place. On most saws, these are two bolts on the side of the engine housing. On some models, the bolts are on top near the spark plug. Your manual will show you exactly where.

Step 2: Loosen the cover bolts until the bar moves

Use your wrench to turn the bolts counterclockwise. You do not need to remove them completely — just loosen them until the bar and chain hang loose and can move freely side to side. This usually takes three or four turns of the wrench on each bolt.

If your saw has a tensioning screw (a separate bolt or knob, often on the side cover), leave it alone for now. You will adjust it after the new chain is on.

Step 3: Slide the old chain off and the new one on

With the bar loose, the old chain should slide off easily. If it does not, loosen the bolts another half-turn. Lift the bar slightly and pull the chain toward you to remove it.

Take the new chain and drape it over the bar, starting at the top. The teeth should point forward (in the direction the bar moves when the saw runs). Feed the chain around the sprocket at the base of the bar, then around the back. The chain should sit in the groove that runs along the bar — if it does not fit, you have the wrong size or pitch.

Step 4: Tighten the cover bolts to hold the bar in place

Once the new chain is on, tighten the cover bolts by hand until they are snug. Do not use the wrench yet — hand-tight is enough at this stage. The bar should not move side to side, but you should still be able to move it slightly by hand.

Check that the chain sits evenly in the bar groove all the way around. If it bunches on one side, loosen the bolts again and reposition the chain.

Step 5: Tension the chain and finish tightening

A properly tensioned chain should sit snug against the bar but still slide by hand when you pull it. To adjust tension, locate the tensioning screw or knob on the side cover — it usually has a plus and minus symbol. Turn it clockwise (plus) to tighten the chain, counterclockwise (minus) to loosen it.

Make small adjustments — a quarter-turn at a time — and check the tension after each one. Once the chain feels right, use your wrench to fully tighten the cover bolts. Tighten them evenly, a quarter-turn on each bolt in sequence, so the bar stays level. When they are snug, stop — over-tightening can crack the cover.

Run the saw for 30 seconds at idle to warm it up, then let it cool and check the tension again. New chains stretch slightly during the first few minutes of use, so you may need to tighten it once more after that first run.

What to do if the chain keeps coming loose

A chain that falls off during use is usually too loose, but it can also mean the bar is bent or the sprocket is worn. Tighten the tension screw first — if the chain still falls off after you have made it as tight as it will go, the bar or sprocket likely needs replacement.

If the chain is too tight, the saw will be hard to start and the motor will strain. You will hear a high-pitched whine or smell burning rubber. Loosen the tension screw when ready and let the saw cool before you run it again.

Frequently Asked Questions

How do I know what size chain to buy?

Check the side of the bar — it usually has a number stamped into it, like "16 in." or "20 in." That is your bar length. The pitch (the distance between the teeth) is also printed there, usually as a decimal like .325 or .375. Write both numbers down before you go to the store, because a wrong size will not fit.

Can I reuse the old chain if I sharpen it?

Yes, if the chain is not bent or cracked. A dull chain can be sharpened with a round file and a file guide, which costs less than a new chain. If the chain has broken links, missing teeth, or visible damage, replacement is your only option.

How tight should the chain be?

Tight enough that it does not sag away from the bar, but loose enough that you can pull it away from the bar by hand. If you cannot move it at all by hand, it is too tight and will burn out the motor. If it sags more than a quarter-inch, it is too loose and will fall off.

What happens if I put the chain on backwards?

The saw will not cut. The teeth point in the wrong direction, so the chain will not bite into the wood. You will know when ready when you try to use it — the saw will make noise but not cut. Turn off the saw, loosen the bolts, and flip the chain around.

Do I need to drain the fuel before I replace the chain?

No. The fuel stays in the tank during a chain replacement. Just make sure the saw is off and unplugged (or the ignition is off on a gas saw) before you start loosening bolts.