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Square Vs. Round Trimmer Line

When you want to cut areas of your lawn your lawn mower cannot reach, reach for a string trimmer. String trimmers use lines traveling at high speeds to cut through vegetation. The type of string you choose for your trimmer might have a small effect on your trimmer's performance.

Replacing Strings

You can buy replacement lines on spools and feed the new replacement lines to your string trimmer. The type of line the string trimmer uses varies, so you will need to find this out before buying replacement lines. Some string trimmers accept either round or square strings. Round and square strings have differences, but they will mostly function similarly enough that you will mostly be choosing your line based on your preferences. Both strings can cut roughly the same kinds of vegetation.

Vegetation Types

The type of line the trimmer uses affects how powerful the string trimmer will be. Round lines work well when trimming grass and light vegetation. When using square lines on light grass, the line will tend to knock the grass out of place, making cutting more difficult. Square string trimmers work better on medium and heavy vegetation, with extra cutting power that allows you to cut through thicker weeds.


Trimmers tend to use round strings the most part. But these strings can sometimes rip the grass, rather than cut it, because that the string does not have edges. Square lines have four sharp edges that increase the trimmer's cutting ability. Round lines do not have an edge.

Wrapping Around Grass

The square strings are more likely to wrap around the grass, getting the string stuck in the grass. This will tend to pull the string trimmer down to the ground, so you will need to pull the string trimmer up from the ground.


MowForce is the lowest-priced trimmer line and this line only comes in a square shape. However, round lines tend to be more durable and will not wear out as frequently, so you can save money by not having to buy string replacements as often.


When not replaced correctly, square lines are more likely to jam than round lines. Also, when square lines hit rocks and other hard objects, they're more likely to break than the round line, which tends to bounce off of these objects.

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