Trimmer line replacement is a five-minute job that costs a few dollars and requires no tools beyond what came with your trimmer
Most string trimmers use a spool system: you wind new line onto a spool, snap the spool back into the trimmer head, and you're done. The exact steps depend on whether your trimmer has a fixed spool or an automatic advance head, but both follow the same basic pattern. You'll need replacement line (usually sold by diameter—0.065 inch and 0.080 inch are most common), scissors or a utility knife, and about five minutes.
The hardest part is usually figuring out which direction to wind the line. Most spools have an arrow molded into the plastic showing the correct direction. If yours doesn't, check your trimmer's manual or the manufacturer's website—winding it backward means the line won't feed properly when you're trimming.
Key Takeaways
- Trimmer line diameter matters: check your trimmer's manual or the old spool to find whether you need 0.065 inch, 0.080 inch, or another size.
- Most spools have an arrow showing which direction to wind the line; winding it backward will cause feeding problems.
- Cut the line to the length marked on the spool—usually 15 to 20 feet—before you start winding.
- After winding, leave a 6-inch tail sticking out so the trimmer head can grab it and feed it through as you trim.
- If your trimmer has an automatic advance head, you may only need to insert a pre-wound spool or feed line through a hole rather than wind it yourself.
Finding the right line diameter for your trimmer
Trimmer line comes in several standard sizes, and using the wrong diameter can damage your trimmer or cause the line to break constantly. The most common sizes are 0.065 inch (used on lighter, electric trimmers) and 0.080 inch (used on gas-powered and heavier-duty trimmers). Some commercial-grade trimmers use 0.095 inch or thicker.
The easiest way to find the right size is to look at your trimmer's manual or the label on the trimmer head itself—most manufacturers print the correct diameter right there. If you've lost the manual, check the manufacturer's website by searching for your trimmer model number (usually stamped on the housing). If you have the old spool, the diameter is often printed on it as well.
Buying the wrong size won't break anything, but the line may not feed smoothly or may snap under normal use. Most hardware stores and online retailers sell trimmer line in pre-wound spools or bulk rolls, so you can pick up the right size while you're there.
Removing the old spool and preparing the new line
Most trimmer heads have a spool cover held on by a single bolt or a snap-on cap. Locate this cover on top of the trimmer head and remove it—usually a quarter-turn counterclockwise with your fingers or a wrench, depending on the design. Once the cover is off, the spool should pull straight out.
Before you wind new line, cut a length from your bulk roll or pre-wound spool. Most spools hold 15 to 20 feet of line, so measure that distance and cut it with scissors or a utility knife. A clean, straight cut makes winding easier and prevents fraying. If you're using a pre-wound spool, skip this step—just insert it into the trimmer head and snap the cover back on.
Inspect the spool itself before you reuse it. If it's cracked, warped, or the grooves are damaged, replace it with a new one (most manufacturers sell spools separately for $5 to $15). A damaged spool won't hold line evenly and will cause feeding problems.
Winding the line onto the spool
Look for the arrow molded into the spool—this shows the direction you must wind the line. Hold the spool in one hand with the arrow pointing away from you, then insert one end of the line into the small notch or hook at the edge of the spool. This notch keeps the line from slipping as you wind.
Wind the line tightly and evenly in the direction the arrow points, keeping tension on the line with your other hand so it doesn't bunch up or overlap. Work your way around the spool in a spiral pattern, filling it layer by layer. Stop when you've wound most of the line, leaving about 6 inches sticking out—this tail is what the trimmer head will grab and feed through as you trim.
If the line starts to slip or bunch, stop and rewind that section. Uneven winding causes the line to feed unevenly and can jam the head. Take your time here—it's the most common place people make mistakes, and redoing it takes less time than troubleshooting a jammed trimmer.
Securing the line and reinstalling the spool
Once you've wound the line, most spools have two small notches or slots on opposite sides where you insert the 6-inch tail to hold it in place while you reinstall the spool. Push the tail firmly into one of these slots so it won't unwind when you're handling the spool. Some spools use a small hook or clip instead—check your spool design and find the tail accordingly.
Insert the spool back into the trimmer head, making sure it seats fully and the shaft goes through the center hole. The spool should sit flat and not wobble. Snap the cover back on or thread the bolt back in and tighten it by hand—don't over-tighten, as this can crack the cover or strip the threads.
Before you use the trimmer, pull the 6-inch tail out of its notch so it's free. The trimmer head will grab this tail and feed it through as you trim. If the tail is still locked in the notch, the line won't feed and you'll think something is broken.
Automatic advance heads and pre-wound spools
Some trimmers, especially newer models, use automatic advance heads that don't require you to wind line yourself. Instead, you either insert a pre-wound spool (which looks like a small cartridge) or feed line through a hole in the trimmer head. These systems are faster and less error-prone, but they cost more to operate because you're buying pre-wound spools instead of bulk line.
If your trimmer has an automatic advance head, check the manual to see whether it uses cartridge spools or a feed-through system. For cartridge spools, you straightforward pop out the old one and snap in a new one—no winding required. For feed-through systems, you thread the line through a hole in the head, wind it around a guide, and lock it in place. The manual will show the exact steps for your model.
Automatic advance heads also feed new line out as the old line wears down, so you don't have to manually bump the head to extend the line. This is convenient, but it also means you'll go through line faster and spend more on replacements over time.
Troubleshooting common winding and feeding problems
If the line won't feed after you've reinstalled the spool, the most common cause is that you wound it in the wrong direction. Check the arrow on the spool again and rewind it if necessary. The second most common cause is that the 6-inch tail is still locked in its notch—pull it out and try again.
If the line feeds but then jams or bunches up, the spool is probably wound unevenly. Remove the spool, unwind it completely, and rewind it more carefully, keeping even tension throughout. Bunched or overlapping line can't feed smoothly and will jam the head.
If the line keeps breaking during use, you may be using the wrong diameter for your trimmer, or the spool itself may be damaged. Check that you're using the correct size for your model. If the diameter is right, inspect the spool for cracks or warped grooves and replace it if necessary.
Frequently Asked Questions
Can I use any brand of trimmer line, or does it have to match my trimmer brand?
Any brand of the correct diameter will work in your trimmer. Trimmer line is a standard product, and a 0.080-inch line from one manufacturer is essentially the same as a 0.080-inch line from another. Buy whatever is cheapest and available at your local hardware store.
What if I wind the line in the wrong direction?
The line won't feed properly—it may not extend at all, or it may jam and bunch up. Unwind it completely and rewind it in the correct direction shown by the arrow on the spool. It's a five-minute fix.
How often do I need to replace the trimmer line?
It depends on how often you trim and what you're cutting. Light residential use might mean replacing the line every few months; heavy use or cutting thick weeds can mean replacing it every few weeks. You'll know it's time when the line becomes noticeably shorter or breaks frequently during use.
Do I need to replace the entire spool, or just the line?
You only need to replace the line. The spool is reusable and will last for years unless it cracks or warps. If the spool is damaged, you can buy a replacement spool separately from the manufacturer for $5 to $15.
What should I do with the old trimmer line?
Trimmer line is plastic and can go in the trash. Some recycling programs accept it, but most don't. Check your local recycling guidelines, and if they don't accept it, throw it away with your regular garbage.