Your trimmer’s owner’s manual sets the size — common residential lines run 0.065 in, 0.080 in, and 0.095 in, while brush work jumps to 0.105 in and up.
For the full breakdown, see our best 0.080 Trimmer Line guide.
There is no universal chart, because every cutting head is built around one diameter. One number decides what your trimmer eats: the cutting line diameter printed in its manual.
What Trimmer Line Size Should I Actually Buy?
Buy the exact diameter your manual specifies and nothing else. Several manuals use the phrase “use only” a single size, and the ones that list a maximum mean it as a hard ceiling, not a suggestion.
Sizing follows tool power and job severity together. Lighter-duty battery and electric trimmers cluster at 0.065 in to 0.080 in, heavier-duty equipment takes 0.095 in and above, and gas trimmers generally tolerate thicker line than their battery cousins. Picking by brand loyalty, spool color, or the thickest line on the shelf ignores the one spec that matters.
The chart below maps the standard diameters to the tasks they’re built for.
| Line Diameter | Typical Job | Trim Like This |
|---|---|---|
| 0.065 in | Light trimming and edging | Grass along foundations, sidewalk edging |
| 0.080 in | General residential cleanup | Routine yard grass and light weeds |
| 0.095 in | Thicker grass and weeds | Overgrown fence lines and ditch grass |
| 0.105 in | Heavy brush | Stalks, saplings, tall dry growth |
| 0.130 in | Heavy brush and commercial work | Sustained cutting on rough ground |
| 0.155 in | Commercial brush clearing | Dense growth with a high-power head |
| 0.060 in | Light electric trimmers | Some compact Husqvarna electric models |
Where To Find Your Trimmer’s Spec
Your manual’s “line diameter,” “replacement line,” or “spool” section holds the answer, and the exact model number on the nameplate gets you to the right version of that manual.
Manufacturers give the spec in different ways. A DEWALT DCST925 manual states a cutting line diameter of 2.0 mm (0.080 in) and directs owners to use only nylon line of that diameter, listing its recommended models DWO1DT801 and DWO1DT802.
Those inch and millimeter figures describe the same physical string, so a spool marked 2.0 mm and one marked 0.080 in are interchangeable on a trimmer that calls for either. If your manual lists approved part numbers, buy those or equivalents the manufacturer explicitly approves — many replacement spools are sold pre-wound for a specific model.
If you’ve confirmed 0.080 in is your number, it pays to check which spools actually hold up in real trimming instead of guessing at the store.
Why Going Thicker Backfires
Upsizing line doesn’t make a trimmer cut harder — it makes the head feed worse and the motor work harder. Manufacturers built the head’s bump-feed mechanism and the motor’s load rating around one diameter, and forcing a thicker string through both breaks that math.
- Feed failure. Oversized line binds inside the spool and stops advancing, so you’re stopping every few feet to pull it out by hand.
- Overheating. A Husqvarna electric trimmer manual warns the motor may overheat and fail if a larger line is used.
- Head damage. WORX’s manual ties the wrong size to improper cutting-head function, and its warning escalates to serious injury.
Never substitute wire, rope, or any non-nylon material, even as a stopgap. Manuals warn those can break loose and become dangerous projectiles, which is a risk no shortcut is worth.
Shape is a separate question from size. Round, twisted, square, and serrated profiles all exist and change how line behaves in the cut, but none of them override the diameter the manual requires — a square 0.095 in line is still the wrong line for a 0.080 in head.
The Frequently Asked Questions
Can I use 0.095 in line in a trimmer that calls for 0.080 in?
No. The manual’s diameter is a compatibility spec, not a starting point. Oversized line binds in the spool, feeds poorly or not at all, and adds load the motor wasn’t rated for — Husqvarna warns of motor overheating and failure from larger line. Buy the listed size, and if you need more cutting power, step up to a trimmer built for it.
Does a thicker trimmer line cut faster?
Not on a trimmer that wasn’t designed for it. Thicker line does cut heavier growth better on the right machine, but on a mismatched head it fouls the feed so you spend more time unclogging than cutting. Match the diameter to the manual first, then match the trimmer to the job.
Where is the line size printed on my trimmer?
Start with the owner’s manual under “line diameter,” “replacement line,” or the spool section. If the manual is gone, read the model number off the nameplate on the housing or handle and pull that model’s documentation. The diameter is also often molded onto the spool cover or the trimmer’s spec decal.
References & Sources
- Family Handyman. “String Trimmer Line Gauge” Supports matching line diameter to tool power and job severity.
- DEWALT. “DCST925 Operator’s Manual” Specifies 2.0 mm (0.080 in) nylon line and approved replacement models.
- eReplacementParts. “Trimmer Line Buying Guide” Explains how diameter, shape, and head design interact.