What Gauge String Trimmer Line To Use

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String trimmers quickly trim and edge your lawn, cut weeds and clear brush. Using the right size and type line increases durability and performance.

A string trimmer is a great tool to care for your lawn and speed up various landscaping chores. Choosing the correct line (thickness/weight, style and material) helps cutting go quicker and lessens the chances of running out of line in the middle of the job.

Before you fire up your trimmer, check the user manual to determine what size lines it can handle. Then think about what you plan to cut.

Low-voltage (up 24 volts) and small gas-powered trimmers (20 cc) work best with medium or small-sized trimmer lines. Thicker lines need more powerful engines that spin fast enough for the trimmer lines to cut through grass and weeds. High-voltage (56 volts or 120-volt corded electric) and heavy-duty gas trimmers (more than 35 cc) can capably handle lines with thicker diameters.

String Trimmer Line Diameter/Weight

String trimmer line comes in three diameters or weights:

  • Light: 0.065- to 0.080-inch line is best for trimming grass around the house and whacking down common lawn weeds from around driveways, walkways and fences.
  • Medium: 0.080 to 0.110-inch line is best for homes with larger lawns, or gardens overgrown with weeds that have tough, heavy stems.
  • Heavy: 0.110-inch and above. Professional landscapers pull this out for big jobs — large lots; commercial spaces; or lawns and gardens with thick grass, woody shrubs and dense underbrush.

String Trimmer Line Shapes

Depending on what you are trimming or cutting, the shape or style string line is as important as the diameter.

  • Round trimmer line works best for home/residential use. The basic shape doesn’t wear or break as easily as other styles, making it more durable for use near concrete, trees and fences. Round line is usually the easiest to replace and has a longer life than other styles. However, round line lacks a cutting edge and rips grass instead of cutting it.
  • Twisted trimmer line has a better cutting edge and is stronger than round line. Normally used to cut back thick, heavy weeds, this trimmer line delivers clean cuts while reducing trimmer vibrations and noise levels. The added strength also helps decrease line wear and breakage when hitting hard surfaces.
  • Squared trimmer line offers four sharp edges that cuts through grass rather than ripping. With this extra cutting power, square trimmer line cuts through thicker weeds easier and works well on modest-to-heavy, thick, overgrown vegetation and undergrowth.
  • Multi-sided (AKA star shaped) trimmer line has multiple edges that quickly and efficiently cut through heavier grass and thicker weeds. However, it breaks easier when striking rocks, stones, concrete and fences.
  • Serrated trimmer line works just like a serrated knife. It easily saws through heavy weeds and grass, leaving a clean cut while reducing your work time.

String Trimmer Line Materials

Most string trimmer line features hardened, monofilament nylon. To strengthen lines and reduce breakage against hard surfaces, many manufacturers add reinforced nylon, aluminum, polymers or other composite compounds.

String Trimmer Line Cost

Heavier and non-round string trimmer line costs more than standard round line. Basic 0.065 round nylon trimmer line can cost less than $8, or you can pay $32 for commercial grade square line.

One highly regarded 0.095 round string line is Husqvarna’s Titanium Force ($14). It easily cuts through thicker grass and denser weeds, breaks less often and runs quieter than most other string trimmer lines.

The Final Word

Most styles and weights are interchangeable, so you can use non-OEM (original equipment manufacturers) line. However, larger/heavier line may not fit every string trimmer. Replace old trimmer line every spring. It could turn brittle over the cold winter and break more easily.

Bob Lacivita
Bob Lacivita is an award-winning ASE and General Motors auto technician, educator and freelance writer who has written about DYI car repairs and vehicle maintenance topics. His work has been featured in The Family Handyman, a Reader's Digest book and Classic Bike Rider magazine. He has been a career and technical educator for 25 years teaching automotive technology, as well as writing state, federal and organizational foundation grants. He also helped design a unique curriculum delivery model that integrates rigorous, relevant academic standards seamlessly into career and technical education.