The Basic Steps to Replace Your 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 spool that twists out. You'll need fresh line (usually 0.080 or 0.095 inches thick, depending on your trimmer model), scissors or a line cutter, and sometimes a small flathead screwdriver to pry open the head cover.

The process is the same whether your trimmer is electric, battery-powered, or gas: stop the engine, let it cool for a minute, locate the spool housing at the bottom of the trimmer head, open it, remove the old line, wind new line onto the spool in the direction the arrow shows, and close the head back up. If you've never done this before, check your trimmer's manual first—the exact opening method varies by brand.

Key Takeaways

  • Most trimmer heads open by twisting counterclockwise or by prying off a plastic cover with a screwdriver or coin.
  • Line diameter matters: check your trimmer's manual or the old spool to confirm whether you need 0.080-inch, 0.095-inch, or another size.
  • Wind new line onto the spool in the direction the printed arrow shows, or the trimmer will not feed line correctly.
  • Leave about 4 to 6 inches of line sticking out from each side of the spool so the trimmer can grab and feed it.
  • If line does not feed after you reassemble the head, the spool is wound backward or the line is not seated in the feed slot.

Identify Your Trimmer Head Type

Before you buy replacement line, you need to know which of the two common head designs your trimmer uses. The easiest way is to look at the bottom of the trimmer head while the engine is off and cool. If you see a large plastic spool visible through a clear or translucent cover, and the cover has a seam running around it, your trimmer uses a fixed spool. If the entire bottom of the head is a solid plastic cap with no visible spool underneath, your trimmer uses a cartridge spool that twists out.

Check your trimmer's manual or the manufacturer's website if you are unsure. The manual will also tell you the correct line diameter for your model. Common sizes are 0.080 inch (for lighter work and electric trimmers) and 0.095 inch (for gas trimmers and heavier brush). Using the wrong diameter can jam the spool or cause the trimmer to feed line poorly.

Open the Trimmer Head

For a fixed spool, look for a seam around the plastic cover. Insert a flathead screwdriver or a coin into the slot along the seam and gently pry the cover off. Work your way around the edge so the cover comes off evenly. Set the cover and any springs or washers aside in a safe place—you will need them to reassemble the head.

For a cartridge spool, grip the spool cap with your hand and turn it counterclockwise. Most cartridge spools unscrew by hand without tools. If it is stuck, wrap a rubber band around the cap for better grip, or use a strap wrench (a tool with a fabric strap that grips without slipping). Once the cap is loose, unscrew it the rest of the way by hand and lift out the spool.

Remove Old Line and Prepare the Spool

Pull any remaining old line off the spool by hand. If line is wound tightly or stuck, use scissors or a line cutter to snip it and peel it away. Wipe the spool clean with a dry cloth to remove dirt, grass, and old line fragments. A clean spool winds new line more evenly and feeds better.

Look at the spool surface. You should see an arrow printed or molded into the plastic showing the direction to wind line. This arrow is critical—if you wind line the wrong way, the trimmer will not feed it. The arrow usually points in the direction the spool rotates when the trimmer runs.

Wind New Line onto the Spool

Cut a length of new line about 20 to 25 feet long. Locate the small notch or slot at the edge of the spool where the line starts. Insert one end of the line into this slot and hold it in place with your thumb. Wind the line onto the spool in the direction the arrow shows, keeping tension on the line as you wind so it sits flat and does not bunch up. Wind slowly and deliberately—rushing causes the line to cross over itself, which jams the feed mechanism.

Continue winding until you have about 4 to 6 inches of line left unwound. This tail of line is what the trimmer head grabs and feeds out as you work. If you wind too much line onto the spool, it will not fit back into the head cover. If you leave too little, the trimmer may not feed line at all.

Once you have wound the line, look for a second notch or slot on the opposite side of the spool. Insert the other end of the line into this slot so both tails are held in place. Some spools have small hooks or clips instead of slots—the line straightforward rests in these, held by the cover when you close the head.

Reassemble the Trimmer Head

For a fixed spool, place the spool back into the head housing. If there was a spring or washer under the cover, place it back on top of the spool first. Align the cover with the seam and press it down firmly all the way around until it clicks or seats flush. You should hear or feel a snap when the cover locks into place.

For a cartridge spool, place the spool back into the head housing and screw the cap back on by hand, turning clockwise. Tighten it firmly but do not force it—hand-tight is usually enough. If the cap is very hard to turn, you may have the spool in backward; remove it, flip it around, and try again.

Once the head is closed, gently tug on both tails of line to make sure they are not pinched under the cover. The line should pull freely. If it does not, open the head again and reseat the line in its slots.

Test the Trimmer and Troubleshoot

Start the trimmer and let it run for a few seconds at idle. Listen for the sound of line feeding—you may hear a slight whirring or clicking as the head advances the line. If line feeds out, you are done. If nothing happens, stop the trimmer and check two things: first, make sure the line is wound in the direction the arrow shows (the most common mistake). Second, make sure both tails of line are actually seated in their slots and not tucked under the spool or cover.

If the trimmer still does not feed line after you recheck these, the spool may be wound too tightly. Unwind a few loops and try again. If line feeds but then jams or stops feeding after a few seconds, the line may be crossing over itself on the spool. Unwind, clean the spool, and wind again more slowly and carefully.

Frequently Asked Questions

What size trimmer line do I need?

Check your trimmer's manual or the old spool for the correct diameter. Common sizes are 0.080 inch for electric and lightweight trimmers, and 0.095 inch for gas trimmers. Using the wrong size can cause feeding problems or damage the spool. If you have lost the manual, search the manufacturer's website using your trimmer model number.

How much line should I wind onto the spool?

Wind until you have about 4 to 6 inches of line left unwound on each side. This tail is what the trimmer grabs and feeds. If you wind too much, the spool will not fit in the head. If you wind too little, the trimmer may not feed line at all. You can always unwind a little and try again.

My trimmer line is not feeding. What did I do wrong?

The most common cause is winding the line backward—check that you wound in the direction the arrow shows. The second most common cause is the line not being seated in its slot. Open the head, make sure both tails are in their slots, and close it again. If it still does not feed, unwind and rewind more slowly.

Can I use any brand of trimmer line?

Yes, as long as the diameter matches your trimmer. Generic line works just as well as name-brand line. Buy from a hardware store, online retailer, or the trimmer manufacturer. Line is inexpensive, so buy a few spools at once so you always have a replacement ready.

How often do I need to replace trimmer line?

It depends on how often you trim and what you cut. Light residential use may need a new spool every few months. Heavy use or cutting thick weeds can use up a spool in weeks. You will know it is time when the line becomes noticeably shorter or stops feeding even after you rewind the spool.