How Do I Know What Size Trimmer Line I Need?

When it comes to maintaining your lawn, the trimmer line you use is just as important as the trimmer itself. Weed eater string, whacker line, or whatever you call it (they’re all the same thing) plays a crucial role in determining how effectively and efficiently you can cut through grass and weeds, so how do you know what size you need?

Trimmer lines come in different diameters ranging from 0.065 inches to 0.155 inches. The size of the line you choose will depend on several factors, including the size of your yard, the type of grass or weeds you need to cut, and the power of your trimmer.

In this article, I’ll explain the different diameters of weed eater lines available on the market and how to determine which size is best for your lawn. I’ll cover all the important topics you need to know about including whether the line size actually matters and discuss if it’s always best to go for the thickest trimmer string you can get.

Understanding Trimmer Line Size

Trimmer lines come in various sizes which always refer to the string’s diameter rather than the length. These range from 0.065 inches to 0.155 inches as follows:

  • 0.065 inches: Suitable for light-duty tasks such as trimming around flower beds or edging along walkways.
  • 0.080 inches: Good for medium-duty tasks such as trimming around trees or bushes.
  • 0.095 inches: Ideal for heavier-duty tasks such as cutting through thick weeds and tall grass in larger yards.
  • 0.105 inches: Great for commercial-grade use or heavy-duty home landscaping projects requiring powerful engines paired with durable strings capable of slicing through even the thickest growths easily without wearing down quickly.
  • 0.155 inches: Used by professionals who require maximum cutting power and durability in dense areas like wet grasses or dense shrubbery and brush where other types might struggle significantly.

As you can see, in general, smaller diameter lines are suitable for lighter-duty tasks such as those found in a small garden. Larger diameter lines are better suited for heavier-duty tasks such as cutting through thick weeds, brush, and tall grass.

Does Trimmer Line Size Matter?

So now you know what the different sizes are, but does it really matter which one you use? 

The short answer is yes.

In fact, when it comes to using a string trimmer, one of the most important factors to consider is the thickness of the line you are going to work with.

This can have a big impact on how well your weed whacker performs. Using the wrong size can result in poor cutting performance and even damage to your equipment. A line that’s too thin may break or wear out quickly, while a line that’s too thick may put too much strain on your engine or cause other issues.

As we already know choosing the right thickness depends on several factors, including the type of trimming you’ll be doing, the density of the grass and weeds you’re cutting, and the power of your string trimmer.

Many homeowners often make the mistake of choosing a line that’s too thin and find themselves having to restring the spool far more than they should have to!

Ultimately, choosing the right size trimmer line for your needs will help ensure that you get optimal performance from your equipment while minimizing the risk of damage or injury. Be sure to consult your owner’s manual or speak with an expert if you’re unsure about which size is best for you!

Can I Use Thicker Trimmer Line? Pros and Cons

When it comes to choosing the right trimmer line for your weed eater, one option to consider is a thicker string. Thicker varieties are typically made from stronger materials and can handle more heavy-duty cutting tasks. However, like any tool, there are both pros and cons to using a fatter cord.


Increased Cutting Power: Thicker trimmer lines have more mass, which means they can cut through thicker grass and weeds with greater ease. This is particularly useful if you have larger areas of land to maintain or if you’re dealing with particularly dense growth.

Longer Lasting: Thicker weed eater strings are generally made from more durable materials than their thinner counterparts. This means that they will last longer before needing to be replaced, which can save you time and money in the long run.

Less Breakage: Because of their increased strength and durability, fatter whacker lines are less likely to break or wear down quickly. This means you’ll spend less time replacing a broken string and more time getting your trimming done.


Higher Cost: Thicker trimmer lines tend to be more expensive than thinner ones due to their higher quality materials and increased durability.

More Strain on Equipment: Using a more bulky line can put more strain on your string trimmer’s engine, which may cause it to work harder and wear out faster over time. However, this only really applies if you are using a line that is thicker than the manufacturer’s recommendation. 

Is Thicker Trimmer Line Better?

While there are some limitations to using a thicker trimmer line for your string trimmer, the benefits may outweigh them depending on your specific needs.

If you have large areas of dense growth that need frequent maintenance or if you want a longer-lasting option that requires fewer replacements over time, then investing in a thicker line may be worth considering.

Be sure to check the manufacturer’s recommendations or speak with someone with some experience before making any changes to ensure that you’re using the best possible equipment for your needs!

What Happens If You Use The Wrong Size Trimmer Line?

Using the wrong size trimmer line can have serious consequences for both your lawn care results and your equipment’s longevity.

If you use a smaller diameter line than what’s recommended for heavier jobs, you’ll find yourself spending more time on each task than necessary because the weaker line will require multiple passes over each area before fully cutting through even moderate growths.

You will also find the string breaks too easily if you’re trying to cut down thicker vegetation. This will slow you down considerably as the weed eater will need restringing far more than if you were using a cord that’s fit for the purpose. With that said, if your trimmer line keeps breaking over and over again, there could be other reasons behind it. You can learn more about these in this article.

On the other hand, if you use a larger diameter line than what’s recommended for lighter tasks like edging around walkways or garden beds where precision is key rather than brute force alone, you could end up damaging your lawn.

If you use a line that’s too thick and then heavy-handedly cut through delicate grasses or plants, they might not recover from such harsh trimming.

Another risk is when accidentally hitting hard surfaces like rocks or concrete edges, the heavier line could cause kickback if you’ve fitted a thicker line than the weed eater is made to take.

In addition to poor performance and potential injury risks from using improper sizes, using a string that’s too thick may result in excessive wear and tear on machines causing damage to parts like the bump head, spool, and guard plate, which could lead to costly repairs over time.

Of course, the instructions that came with your model are usually helpful in determining what size of string will work best with your particular weed eater. By checking carefully how fat the line can be for the spool on your machine, you’ll ensure that you get optimal cutting power and efficiency while avoiding any potential damage to both your equipment and landscaping.

What Trimmer String Do Professionals Use?

Many professional landscapers and lawn care experts will often swear by a specific type of trimmer line that they use all the time. Whatever brand they buy, it’s always going to be a type that’s designed for heavy-duty use but may differ in diameter and style.

When it comes to line thickness, professionals often use a diameter of between 0.080 and 0.105 inches. This is because commercial-grade thicker lines are more durable and better equipped to handle heavy-duty cutting tasks, which is necessary for tackling larger areas or dense growth.

Additionally, a thicker line can help save time and money as it typically lasts longer before needing to be replaced.

Note that the pros use powerful gas-driven weedeaters that are made to take the larger strings and can handle the toughest of clearing jobs.

But the size is not the only thing that makes professional grade lines different from standard options. Lawn care experts often use twisted or serrated trimmer lines rather than square or round ones.

What Are The Different Types Of Weed Eater Line?

When it comes to choosing the right trimmer line for your needs, it’s important to understand that there are several different types available. 

Each type has its own unique characteristics and benefits, so it’s worth taking some time to learn about your options before making a decision. Here are the most popular varieties you can buy at the store:

  1. Round Trimmer Line – This is the most common type of trimmer line and is suitable for most general trimming tasks around the yard. It is made from nylon and is typically available in most thicknesses. Round strings are the least durable and are best for light weed clearing and trimming low to medium-height grass.
  2. Square Trimmer Line – Square strings have a square cross-section instead of a round one, which helps them cut through grass more efficiently. They tend to wear down more slowly than round lines, but they may not be suitable for all types of trimmers.
  3. Twisted Trimmer Line – As the name suggests, this type of line has a design that looks like a metal cable with strands twisted together and provides extra cutting power and durability compared to round lines. They are great for heavy-duty jobs like clearing out dense vegetation or large areas of land.
  4. Serrated Trimmer Line – Serrated lines have teeth-like serrations on their edges, which helps them cut through tough vegetation like woody weeds or thick brush better than other types of lines.
  5. Star-Shaped Trimmer Line – usually made in a 5-pointed star cross-section, these lines cut through grass and weeds quickly and cleanly while also reducing wear on the line itself.

Each type of trimmer line has its own advantages and disadvantages depending on the job at hand, so it’s important to choose carefully based on your specific needs.

While twisted or serrated trimmer line is certainly effective for heavy-duty applications like commercial landscaping, it may not be necessary for most homeowners. If you have a smaller yard or only need to do light trimming around your property, a standard round or square-shaped line should suffice.

That being said, if you have particularly tough grass or weeds to deal with, upgrading to a twisted or serrated string could be worth considering. These can really save time and effort when tackling stubborn growth and provide more efficient cutting power overall. 

If you need more help choosing the right trimmer line, check out this detailed guide I wrote on the topic. 

Conclusion: Finding the Best-Sized Trimmer Line for Your Lawn Care Needs

I hope you’ve found this comprehensive guide to choosing the right size string useful and you now know that it requires careful consideration based on your own individual needs.

Whether doing light trimming work around garden beds or undertaking heavy-duty landscaping projects there are plenty of options to choose from, especially when you take into account the different types of cross-sections available as well.

For most homeowners with average-sized yards, sticking with a standard round or square-shaped trim line of medium thickness should do just fine. However, if you’re dealing with a particularly dense growth or plan on using your string trimmer frequently over larger areas, investing in a higher-quality, thicker twisted or serrated trim line could pay off in the long run.

Just be sure to choose wisely to avoid costly mistakes such as damaging your machine or mistakenly ripping through delicate plants!

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!

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