Fishing Line Diameter Database: Compare Braid, Mono and Fluorocarbon Sizes
Use this fishing line diameter database to compare braid, monofilament, fluorocarbon, fluorocarbon leader, and hybrid fishing line by brand, model, pound test, and actual diameter. Line diameter matters because two lines with the same pound test can be very different thicknesses, which changes how much line fits on a reel and how much backing you need.
In short: pound test tells you breaking strength, but diameter tells you how much space the line takes up on the spool. If you are trying to calculate reel capacity, compare equivalent lines, or choose backing, diameter is usually the more useful number.
Fishing Line Diameter Database
Find Equivalent Line Diameter
| Brand | Model | Type | lb | Diameter (in) | Diameter (mm) |
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| Brand | Model | Type | lb | Diameter (in) | Diameter (mm) |
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Looking for Japanese PE line sizes? Check out the PE Line Diameter Database to compare PE ratings, braid diameters, pound test, and strand count.
Why Fishing Line Diameter Matters
Fishing line diameter is one of the most important numbers for reel capacity. A thinner line takes up less space on the spool, so more yards fit. A thicker line takes up more space, so fewer yards fit. This is why a reel might hold much more 10 lb braid than 10 lb monofilament, even though both lines are labeled as 10 lb test.
Diameter also affects casting distance, lure action, sink rate, knot size, and how much backing is needed underneath your main line. When you are filling a spinning reel, baitcaster, trolling reel, or saltwater reel, using actual line diameter gives a more accurate estimate than using pound test alone.
Pound Test vs Line Diameter
Pound test and line diameter are not the same thing. Pound test is the line’s rated breaking strength. Diameter is the physical thickness of the line. Two fishing lines can both be labeled 10 lb test but have completely different diameters depending on the material, brand, coating, and construction.
For example, 10 lb braid is usually much thinner than 10 lb monofilament or 10 lb fluorocarbon. That means a reel rated for 10 lb mono will usually hold a much longer length of 10 lb braid. This is why line diameter is the better number to use when calculating reel capacity or backing.
How to Use This Line Diameter Database
Use the search box and table above to find a fishing line by brand, model, line type, pound test, or diameter. Once you find the line you want to use, look at the listed diameter in inches or millimeters.
That diameter can help you compare similar lines, find equivalent line sizes, or calculate reel capacity more accurately. For example, two braided lines may both be labeled 10 lb test, but if one has a smaller diameter, more of that line will usually fit on the reel.
For the most accurate setup, find your line diameter here first, then use the ReelCalc fishing reel backing calculator to estimate how much backing and main line will fit on your spool.
How Line Diameter Helps With Reel Backing
Backing calculations are more accurate when you know the diameter of both lines: the backing line and the main line. If you are using monofilament backing under braided line, the calculator needs to estimate how much spool space each line takes up.
Pound test alone is not enough because 10 lb braid, 10 lb mono, and 10 lb fluorocarbon can all have different diameters. Using actual line diameter gives a better estimate of how much backing to add before filling the rest of the spool with your main line.
If you do not want to use backing, you can also use the calculator’s Capacity Mode to estimate how much of one line will fit on the spool.
Common Fishing Line Diameter Questions
Is fishing line diameter more important than pound test?
For reel capacity, yes. Pound test tells you the rated breaking strength of the line, but diameter tells you how much physical space the line takes up on the spool. If you are calculating how much line fits on a reel, diameter is usually the more useful number.
Why does braid fit differently than mono?
Braid is usually thinner than monofilament at the same pound test. Because thinner line takes up less space, a reel will usually hold more yards of braid than mono, even if both lines have the same pound-test rating.
Are fishing line diameters exact?
Line diameters are best treated as reference numbers. Diameter can vary by brand, coating, material, manufacturing method, and how the line is measured. For reel capacity and backing estimates, manufacturer-listed diameter is still much better than guessing by pound test alone.
Can I use this database with the ReelCalc backing calculator?
Yes. Find the diameter of your main line or backing line in the database, then enter that diameter into the ReelCalc calculator. This helps estimate reel capacity and backing more accurately.
What if my reel uses PE ratings?
Use the PE Line Diameter Database or PE Line Capacity Calculator. PE sizing is common with Japanese braided line and JDM reel capacity ratings, and it does not convert perfectly to pound test.