The Basic Process for Replacing Trimmer Line
Replacing trimmer line takes about five minutes once you know where the spool is and how your trimmer head opens. Most trimmers use one of two designs: a fixed spool that you unwind by hand, or a cartridge that twists out or clicks free. You'll need fresh line that matches your trimmer's diameter—usually .065, .080, or .095 inches—and nothing else. The line itself costs a few dollars and lasts through several yards of cutting before you need to wind it again.
The hardest part is usually just locating the release button or figuring out which direction to turn. Once you open the head, winding new line takes longer than removing the old. Most people finish the whole job in under ten minutes after the first time.
Key Takeaways
- Trimmer line diameter varies by model, so check your manual or the old spool to buy the right size before you start.
- Most trimmer heads either twist counterclockwise to open or have a release button on the side—your manual will show which.
- Wind new line evenly and tightly around the spool in the direction marked by an arrow, leaving 4 to 6 inches free at the end.
- Thread the free end through the eyelet or guide hole before closing the head, or the line won't feed out when you need it.
- Test the trimmer over a bucket or outside before you use it, because loose wrapping causes the line to tangle or not feed.
Identify Your Trimmer Head Type and Find the Right Line
Before you buy anything, look at your trimmer head and find the model number. It's usually stamped on the plastic housing or printed on a label. Write it down and check your manual or the manufacturer's website to confirm the line diameter your trimmer uses. Common sizes are .065 inch (thin, for light grass), .080 inch (standard), and .095 inch (thick, for brush). Buying the wrong size means the line won't fit in the spool or won't feed properly.
If you've lost the manual, look at the old spool itself—many have the diameter printed on the plastic. You can also bring the trimmer to a hardware store and ask staff to match it. Buy a spool or pre-wound cartridge of the correct size. Pre-wound cartridges cost more but save you the winding step; fixed spools cost less but require you to wind the line yourself.
Open the Trimmer Head and Remove the Old Spool
Unplug the trimmer or remove the battery so it cannot start while you work. Look at the trimmer head—you'll see either a large plastic knob in the center or a small button on the side. If there's a knob, grip it firmly and turn counterclockwise (lefty-loosey). It usually takes two or three full turns before the head separates. If there's a button, press it while pulling the spool straight up and out.
Once the head is open, pull out the old spool or cartridge. If line is still wound on it, you can discard it or save the spool if it's reusable. Wipe out any grass clippings or dirt from inside the head with a dry cloth. Check that the eyelet—the small hole where line feeds out—is clear and not cracked. If it's damaged, the trimmer head may need replacement.
Wind New Line on a Fixed Spool
If you bought a pre-wound cartridge, skip this section and go to the next one. If you have a fixed spool, you'll wind the line yourself. Look for an arrow printed on the spool that shows the winding direction. Cut a length of line about 20 to 25 feet long from the spool you bought. Tie one end to the small anchor notch on the trimmer spool—there's usually a slot or hook designed for this.
Hold the spool steady and wind the line tightly and evenly in the direction the arrow points. Keep tension on the line as you wind so it doesn't bunch or overlap. Wind until you have about 4 to 6 inches of line left free. Tuck the free end into the slot or notch on the edge of the spool so it doesn't unwind. The line should be snug but not so tight that it's hard to turn the spool by hand.
Install the Spool and Thread the Line
Set the wound spool back into the trimmer head, making sure it sits flat and the center post goes through the hole. If you're using a pre-wound cartridge, just push it straight down until it clicks or seats fully. Now you need to thread the free end of the line through the eyelet or guide hole on the trimmer head. This is the small opening where line feeds out when you're cutting. If you skip this step, the line won't come out when you need it.
Pull the free end of line through the eyelet and leave about 2 inches sticking out. Close the trimmer head by turning the knob clockwise (righty-tighty) until it's snug, or by pushing the spool down and clicking it into place. Don't over-tighten—you only need it tight enough that it won't come loose during use. If the head is hard to close, the line may be in the way; open it again and reposition the free end.
Test the Trimmer and Trim the Line to Length
Plug the trimmer back in or reinstall the battery. Hold it over a bucket or go outside to a safe area away from people and pets. Tap the trimmer head gently on the ground a few times—this is how most trimmers feed new line out automatically. If line doesn't come out, the free end may not be threaded through the eyelet. Stop, unplug the trimmer, and check that the line is actually going through the hole.
Once line feeds out, let it run for a few seconds to see how it behaves. The line should spin smoothly without tangling or bunching. If it tangles, the spool was wound too loosely or unevenly. You may need to open the head and rewind it more tightly. Once the line is feeding cleanly, use the trimmer's cutting edge or a utility knife to trim the line to the correct length—usually about 2 inches shorter than the diameter of the cutting head, so it doesn't hit the guard.
Troubleshoot Common Winding and Feeding Problems
If the line won't feed out even after tapping the head on the ground, the most common cause is that the free end isn't threaded through the eyelet. Open the head and check. The second most common cause is that the line was wound too loosely, so there's no tension to push it out. Rewind it more tightly and try again. If the line tangles or bunches when it does feed, the spool was wound unevenly or the line overlapped itself. Unwinding and rewinding takes time, but it's the only fix.
If the trimmer head won't close all the way, something is blocking it—usually the free end of line. Open it again and tuck the line end further into its notch or slot. If the knob is hard to turn, you may have over-tightened it; back it off a quarter turn. If the eyelet is cracked or missing, line won't feed out no matter how well you wind the spool. In that case, the trimmer head itself needs replacement, which is usually cheaper than buying a new trimmer.
Frequently Asked Questions
How do I know what diameter line my trimmer uses?
Check your trimmer's manual or look for a label on the trimmer head or motor housing. If you can't find either, look at the old spool—the diameter is often printed there. Common sizes are .065, .080, and .095 inches. If you're still unsure, bring the trimmer to a hardware store and staff can match it for you.
Can I use a different diameter line than what the manual says?
No. Using the wrong diameter can cause the line not to fit in the spool, not to feed properly, or to break too easily. Stick to what your manual specifies. If you can't find the manual, match the old spool.
What if I wind the line the wrong direction?
The line won't feed out, or it will feed very slowly. Look for the arrow on the spool showing the correct direction and rewind it. It takes a few minutes but is the only way to fix it.
How often do I need to replace the trimmer line?
It depends on how much you use the trimmer and what you're cutting. Light grass cutting might let you go several months. Heavy use or cutting thick weeds can wear through a full spool in a few weeks. You'll know it's time when the line gets too short to cut effectively or breaks frequently.
Do I have to wind the line myself, or can I buy it pre-wound?
You can buy pre-wound cartridges that you just drop into the trimmer head—they cost more but save you the winding step. You can also buy bulk line and wind it yourself, which costs less but takes a few minutes. Either way works fine.