Buy Fishing Line Based on Diameter [+ Chart and Converter]

Fishing Line Diameter Chart and Converter

Knowing what fishing line to use can make or break your fishing experience.

For novice anglers, this may seem confusing, because the same fish specie can be caught on various line diameters, depending on the conditions and technique.

Of course, there is no “one line fits all” however, there are some recommendations that can be used in various conditions for certain species. What makes it confusing is fishing line specifications. Some use diameters in millimeters while others use lb.

All of this can result in choosing the wrong lines and going home empty handed. Line thickness affects line visibility, lure control, and a lot more.

To make these calculations easier, I decided to explain the basics, include a fishing line diameter chart, and answer some common questions.

This can also be a good reminder for experienced anglers who may need to refresh their knowledge.



Get my FREE fishing e-book where you will find my PRO Tips!

Free Fishing Ebook

How do I Know What Diameter to Buy? [Braid, Mono or Fluorocarbon]

Fishing line width chart can help you here but before we get to it, I have to explain some theoretical basics.

First of all, you need to consider your fishing gear and size of the fish you are trying to catch. Here are some basics about fishing line.

  • Mono lines are great for lighter setup and go well with spinning gear. For the same strength, mono lines have larger diameter than braided lines. This is a very popular type for beginners.

  • Braided lines are better for heavier setup, and for baitcasting reels due to incredible strength. For the same strength they have lower diameter than mono. I wouldn’t advise you to use too thin braided lines with baitcasters and with light lures as that leads to tangles.

  • Fluorocarbon lines are also made from one strain of nylon like mono, but are stronger and stiffer. When compared to mono, 14 pound test fluorocarbon line for example has the same diameter as 9.6 mono.

  • Copolymer fishing line is a line that combines two different nylons, and it is much thinner which means you can spool more length.

Your rod also affects this choice. For heavy and long rods, you will need larger diameter lines.

Before you decide what diameter to use, you should consider your potential catch size.

The bigger fish you are targeting, the bigger diameter you will need. But, be careful not to exaggerate here.

Fishing Line Diameter Chart Converter - What Size

How are Fishing Lines Specified? In Various Ways!

In terms of fishing line, different line types can be specified in various ways, often more than one. To clarify this, here are the basic explanations of the most common ways:

  • LBLb (and sometimes Kg) is a line specification that tells you the strength of your line. It tells you under how much pressure it may break. Luckily, majority of the lines actually break well above the stated rating, especially braided ones.

    Of course, you must think about knot strength too here, as it can significantly reduce your overall setup strength. Two lines with same strength rating can have different diameters.

  • MM – This is a straightforward line specification that tells you what the line thickness is. It does not tell you its breaking strength. In mono lines, mm specification is absolutely correct, however when it comes to braided lines, there are some concerns about the measuring system as the pressure can flatten the line and “lower” its diameter. Sometimes, the diameter can be marked in inches too.

  • PE – This specification originates from Japan, and PE comes from polyethylene lines. Lines are specified in diameter and reels are specified with how many meters of a certain diameter can fit on it. Keep in mind that PE measures diameter only and not a braking strength. So, two lines with same PE may actually have different breaking strength. Additionally, although it describes diameter, PE is not specified in mm or inch.

Easy Line Diameter Chart and Converter [in Lb and Mm]

To wrap this theory up, here I will include fishing line diameter chart in lb and mm so that you can see how it all looks like. This chart is also a simple converter.

Weather you need braided, monofilament or fluorocarbon fishing line diameter chart, here you can find it all.

Diameter (mm) PE Mono (lb) Braided (lb) Fluoro (lb)
0.100 0.4 / 6 /
0.128 0.6 / 8 /
0.148 0.8 2.2 10 /
0.165 1.0 3.5 15 4
0.205 1.5 4.4 20 6
0.235 2.0 5.8 25 8
0.260 2.5 6.4 30 10
0.285 3.0 8.8 35 12
0.310 3.5 9.6 40 14
0.330 4.0 12.2 50 15
0.370 5.0 15.9 60 17
0.405 6.0 17.4 80 20
0.470 8.0 25.6 100 28
0.535 10.0 32.7 120 36
0.570 12.0 37.1 140 40
0.620 14.0 44.4 160 46

Here I listed the most common sizes/ratings, however those are not the only ones.

As you can see, there is a “pattern” so you can assume the diameter of let’s say PE 7 or 11. Differences between some are so small that it is impossible to recognize it by looking. But of course, if you compare a few sizes difference, it is noticeable.

What is extremely important to say is that it also depends on a manufacturer, quality of their materials, process of making, and other factors.

Two manufacturers can both have 0.205 mm diameter line of the same type, but the breaking strength between the two can differ. It most frequently happens in fluoro lines and for those you will find all kinds of specs for seemingly identical lines.

There is a wide range of lines to choose from and you should study it thoroughly. Whether you are choosing big 40 pound test braided line or a smaller diameter 12 pound test monofilament line, make sure to choose a good brand.

Fishing Line Diameter Chart Converter - Different Lines

FAQ's about Best Fishing Line Diameter:

Now when you know mm to lb fishing line conversion, here are some answers that could help you plan your next fishing trip!

Does the Diameter of Fishing Line Matter?

All info mentioned above is, let’s say, “technical”. But real life has a lot of influence too, and diameter of the line matters a lot in many aspects, not just how it goes with your gear. Most importantly, diameter affects presentation.

Low diameter lines are less visible and great for clear waters. So, if you are fishing for trout in a crystal-clear creek, feel free to downsize.

Thicker lines are excellent in heavy cover and rough areas where there is a chance that your thin line may break. In such heavy cover, it won`t be that visible, and it will have larger abrasion resistance.

Line diameter affects how much line length can you fit onto your reel. You should always follow manufacturers recommendations on reel capacity not to overfill your spool. The thinner the line, the more you will be able to spool.

Lure weight also affect line diameter. Heavy lures go better with larger diameter lines.

In addition to all this, you can use fluorocarbon leader or monofilament leader line and braided mainline, which means that your setup will vary in diameter.

What Diameter Fishing Line for Bass?

Bass can be caught on variety of sizes and line diameters; however, some recommendations would be around 8 to 14 lbs mono in most conditions, 15 to 20 for heavy cover, or if you plant to switch to braid, you can go all the way to 30 or even 50 lb!

From the chart, you can see that when converted to diameters, this means the following:

“Normal” conditions mono - 0.285 to 0.330 mm

Heavy cover mono - 0.370 to 0.435 mm

Braided - 0.260 to 0.330

What Diameter Fishing Line for Trout?

Trout live in very clear waters and see your line well. As an angler, you should make your presentation as invisible as possible.

Mono - 0.165 to 0.235 mm

Fluoro - 0.165 to 0.205 mm

Very heavy and large fish - 0.310 mm mono or 0.260 mm fluoro

What Diameter Fishing Line for Carp?

Carp can be heavy and fight hard. Depending on a size of a fish you are targeting, and line type you are preferring, you can go with different main line diameters.

Mono - Usually anglers use 10 to 20 lb, which is 0.310 to 0.435 mm in diameter. That can cover many fishing situations for beginners.

Fluoro - Most often anglers use 0.260 or 0.310 mm.

What Diameter Fishing Line for Catfish?

And lastly, we have catfish. Some of them are known for living in low visibility conditions so line diameter in terms of presentation is less important than with trout or easily spooked carp.

For a beginner and some average sized channel catfish use the following:

Mono - 0.330 to 0.470 mm

Fluoro - around 0.370 mm

Fishing Line Diameter Chart Converter - Braid on Reel


Fishing line diameter is important because of various reasons, and the most important one is presentation. As explained above, it also affects abrasion resistance, tangling, and compatibility with all your equipment.

To easily convers lb to mm, I created the fishing line diameter chart which can help you find out the necessary diameters for a second.

Of course, diameter – strength ratio can vary among manufacturers, and you should always read detailed specifications stated on the product.

About Me

Slo-fishing - About Us


I am Siniša Pintar (friends call me Sina), the guy behind and eBook writer. This site is base camp for fishing enthusiasts from all over the world. I love fishing and want to share all my stories, knowledge and my experience with any and all potential anglers. Read more ...

Affiliate Disclaimer:

Slo-fishing is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. We also participates in eBay Partner Network, FishingBooker, ClickBank and Teespring affiliate programs. We are compensated for referring traffic and business to these companies.