How to Choose String Trimmer Line Size

How to Choose String Trimmer Line Size

ByKen

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If you are asking how to choose string trimmer line size, start with the diameter your trimmer head takes, not with the spool you already have. The manufacturer states the diameters each head takes in its own pages. The sources we opened show diameters such as 0.080 inch and 0.095 inch. A line that does not match the model can cause feeding problems or breakage. This guide shows how the sources state the diameter and what they do not say.

Quick answer

  • Use the diameter approved for your model. Husqvarna’s 122L page says its T25 head accommodates 0.065-inch, 0.080-inch or 0.095-inch line.
  • Line that does not match the model can cause feeding problems or breakage, according to Husqvarna’s reload guide.
  • For typical yard conditions, the 122L page recommends 0.095-inch line. That is a recommendation for one head, not a default for every trimmer.
  • The sources we opened do not say where the diameter is printed on a spool or in a manual, so this guide does not say either.

Where the diameter is stated

The manufacturer’s line listings give a diameter and a length for each spool. The Husqvarna Titanium Force listing is one example. It shows a series of spool variants, each with a line diameter in inches and a line length in feet. The table copies the stated figures and shows the length that goes with each diameter.

Line diameter (as listed) Line length on a listed variant Source
0.08 in 208 ft and 1,200 ft Husqvarna Titanium Force listing
0.095 in 100 ft, 140 ft and 200 ft Husqvarna Titanium Force listing
0.105 in 115 ft and 690 ft Husqvarna Titanium Force listing
0.13 in 76 ft, 150 ft and 450 ft Husqvarna Titanium Force listing

Read the length as the amount of line on the spool, not as a sign of the right diameter. A longer spool of the wrong diameter is still the wrong line for the head.

Head limits from the manufacturer

A head sets the range of line it can take, so check the head before you pick the diameter. The sources we opened give the head limits for three Husqvarna heads.

Head or model Line the source states Source
122L, with the T25 head 0.065-inch, 0.080-inch or 0.095-inch line Husqvarna 122L page
Rapid Replace bump-feed head (general listing) 0.065 to 0.105 inch line, and up to 22 ft of 0.095-inch line Husqvarna Rapid Replace page
Rapid Replace bump-feed head for 220iL and 320iL Up to 18 ft of 0.080-inch line Husqvarna 220iL and 320iL page

For the 122L, the page is direct: the T25 head accommodates three diameters, and it recommends 0.095-inch Titanium Force line for typical yard conditions. That gives you a range to work inside, and a recommended size inside the range. The general Rapid Replace listing says the head takes line from 0.065 to 0.105 inch. The 220iL and 320iL listing gives a different capacity, 0.080-inch line, so the same head name does not mean the same line limit across models.

If your model is not in these listings, do not guess from a neighbour model. Check the manual or the head’s own listing for the approved diameter. The sources we opened do not cover every head, and the manuals for some other brands are PDF files that we could not open, so this guide does not state their line sizes.

Read the number as inches

The Husqvarna pages state line sizes in inches, using forms such as 0.095-inch and 0.095 in. This guide keeps those inch figures as the sources state them. It does not convert them to millimetres, because the sources we opened do not give that conversion. When you compare a spool with your head’s limit, compare inch to inch.

Two numbers in the listings do different jobs. The diameter is the number that decides fit. The length is the amount of line on the spool. Do not treat a long spool as a different size.

If you want to check the chosen line against the head before you install it, the reload steps in the Husqvarna support guide are the place to start. They describe where the line goes and how the spool winds, and they list the line size as a separate item to check. The next section covers what happens when the size is wrong.

What goes wrong with the wrong size

The Husqvarna reload guide puts the size in the setup list, next to the power step. It says the trimmer line must be the correct thickness for your model, and it warns that “Using the wrong line size can cause feeding problems or breakage.” The same guide lists “Incorrect line thickness” among its common problems. The guide does not say what each wrong size looks like, so do not treat its problem list as a diagnosis for your head.

The Husqvarna reload guide also says that winding in the wrong direction is the most common mistake. That is a separate issue from the diameter, but it is easy to confuse with a wrong size when the line will not feed. Check the diameter first, then check the winding direction against the arrows on the spool.

Bump-feed heads still need the right size. The Rapid Replace listing says you feed the head with line in the stated range, then twist. A line outside that range is outside what the listing states the head takes.

Safety before you change the line

Disconnect the power before you open a trimmer head. The Husqvarna reload guide lists “Disconnect power (battery or spark plug)” under Before starting. The Husqvarna head replacement guide says the same for battery trimmers: “If using the battery-powered product, take out the battery. If using the petrol-powered product, turn off the product.” The OSHA eTool on power tools gives the general rule: “Disconnect tools when not in use, before servicing, and when changing accessories such as blades, bits, etc.”

This guide does not give blade or cutting-head removal steps. The power-off rule above applies before any line change.

Match the line to the head: a four-step check

Use this check when you buy line. It uses only the figures stated above.

Step 1: Find the approved diameter for your model in the manual or the head listing. Call it the head limit.

Step 2: If the head limit is a single size, buy that size. If the head limit is a range, as the 122L and the general Rapid Replace listing show, pick a size inside the range. For the 122L, the page recommends 0.095-inch line for typical yard conditions.

Step 3: Compare the diameter on the spool, package or listing with the head limit from Step 1. The sources we opened do not say where the diameter appears on a spool.

Step 4: If the number does not match, do not load the line. A line outside the head limit is the wrong size for that head.

If your trimmer is a Ryobi One+ model, the Ryobi One+ weed eater string post is the related page on this site. For changing the string on a Ryobi 40V trimmer, see changing the string on a Ryobi 40V trimmer. Check the diameter for your head in either case before you buy. If you are still choosing between trimmer brands, the Greenworks and EGO string trimmer comparison covers that choice, and the head limit still decides the line.

How we chose

The seven pages in the sources list are the ones this guide cites, and we opened each one on 2026-10-22. Six are Husqvarna pages: the Titanium Force listing, the 122L page, the reload support guide, the two Rapid Replace listings, and the head replacement support article. The OSHA eTool is the general power-tool rule.

The Husqvarna pages are manufacturer pages, so they show only the sizes that maker states. We picked them because they state a diameter in a form we could quote word for word. We did not check the diameter against any other brand, and we did not rank line or trimmers. Every line size in this guide is quoted from a page we opened.

What we could not verify

We could not verify where the diameter is printed on a spool or in a manual. The sources we opened do not describe that label. We could not verify the diameter for any non-Husqvarna trimmer, because the manuals we found for those models are PDF files that we could not open. We could not check how a heavier line affects the motor or the head, because the sources we opened do not say.

What the sources do not say

The sources we opened do not give a line diameter for any trimmer from a brand other than Husqvarna. They do not say where the approved diameter is printed on a spool or in a manual. They do not say which diameter suits light trimming, a particular edging task or a particular lawn type. They do not state a conversion to millimetres. Where a size is not stated, this guide does not give one.

FAQ

Can I use a thicker line than my trimmer’s rating?

The sources we opened say the line must match the model, and that the wrong size can cause feeding problems or breakage. They do not give a rule for a thicker line on any specific trimmer. Check the approved diameter for your model before you buy a thicker line.

What line size does a Husqvarna 122L take?

The Husqvarna 122L page says its T25 head accommodates 0.065-inch, 0.080-inch and 0.095-inch line. It recommends 0.095-inch Titanium Force line for typical yard conditions. That is the page’s recommendation for this head, so check the head before you buy.

What line does a Husqvarna bump-feed head take?

The general Rapid Replace listing says the head takes line from 0.065 to 0.105 inch, and it can hold up to 22 ft of 0.095-inch line. The 220iL and 320iL Rapid Replace listing says that head can hold up to 18 ft of 0.080-inch line. The two pages give different capacities, so read the one for your model.

Where do I find the right diameter?

The Husqvarna reload guide says the line must be the correct thickness for your model. The sources we opened do not say where that number is printed on a spool. Check the manual or the head listing for the approved diameter, and match the spool to that number.

Do I need to disconnect the battery before changing the line?

Yes. The Husqvarna reload guide lists “Disconnect power (battery or spark plug)” as the first step. The Husqvarna head replacement guide says to take the battery out on a battery trimmer, and the OSHA eTool gives the general rule to disconnect tools before servicing.

Is 0.095 inch the standard size?

No. The 122L page recommends 0.095-inch line for typical yard conditions, and the Titanium Force listings include several 0.095-inch variants. Neither makes 0.095 inch a universal standard. Some heads take a range of diameters, as the 122L and general Rapid Replace listings show, so match the line to your head.

Bottom line

Match the diameter to the head limit your manual or listing states, and disconnect the power before you change the line. If the head takes a range, the 122L page’s 0.095-inch recommendation is a starting point, not a rule.

Sources

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