Diameter is the number that decides how much line fits on your reel, how far you can cast and how deep your lure runs — more than the pound test does. Here is the lb-to-mm conversion for all three line types.
| Strength | Mono (mm) | Fluoro (mm) | Braid (mm) | Braid PE | Mono (in) |
|---|---|---|---|---|---|
| 4 lb | 0.20 | 0.19 | — | — | 0.008 |
| 6 lb | 0.24 | 0.23 | 0.11 | 0.6 | 0.009 |
| 8 lb | 0.27 | 0.26 | 0.13 | 0.8 | 0.011 |
| 10 lb | 0.30 | 0.29 | 0.15 | 1.0 | 0.012 |
| 12 lb | 0.33 | 0.32 | 0.17 | 1.2 | 0.013 |
| 15 lb | 0.37 | 0.36 | 0.19 | 1.5 | 0.015 |
| 20 lb | 0.44 | 0.42 | 0.23 | 2.0 | 0.017 |
| 25 lb | 0.50 | 0.47 | 0.26 | 2.5 | 0.020 |
| 30 lb | 0.55 | 0.52 | 0.28 | 3.0 | 0.022 |
| 40 lb | 0.63 | 0.61 | 0.32 | 4.0 | 0.025 |
| 50 lb | 0.71 | 0.69 | 0.36 | 5.0 | 0.028 |
| 65 lb | 0.81 | 0.80 | 0.42 | 6.0 | 0.032 |
| 80 lb | 0.91 | 0.90 | 0.46 | 8.0 | 0.036 |
Figures are typical published values. Diameter varies between brands and even between product lines within a brand — a "thin" 20 lb mono can be noticeably thinner than a standard one at the same rating.
Three things follow from diameter rather than strength. Capacity: how much line fits on the spool. Distance: thinner line casts further because it has less air resistance and less friction through the guides. Depth: thinner line catches less water, so a lure or sinker runs deeper on the same weight.
This is why braid changed so much of fishing. At the same pound test it is roughly half the diameter of mono, which means roughly twice the line on the spool and access to depths mono cannot reach.
PE is the Japanese braid sizing system and it is based on diameter, not strength. The useful rule of thumb is diameter in millimeters is roughly 0.165 × the square root of the PE number, so PE 1.0 is about 0.165 mm and PE 4.0 is about 0.33 mm.
Because PE describes diameter, the pound test attached to a given PE varies between brands depending on how many strands the braid has. PE 2.0 is usually around 20 to 30 lb. When in doubt, buy by diameter and check the stated breaking strain.
Buy by diameter first, strength second — and keep the range so you can match the reel.
About half the diameter of 20 lb mono. Roughly twice the capacity, longer casts and far better bite detection.
Check current price on Amazon →Nearly invisible underwater and more abrasion-resistant than mono. The standard leader material over a braid main line.
Check current price on Amazon →Still the best value all-round line, and its stretch forgives a great deal on a baitcaster. Cheap enough to change often.
Check current price on Amazon →Line put on with no tension beds down under load and digs into itself. A spooler with tension control fixes the most common line problem there is.
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Diameter drives capacity, distance and sink rate together. The line diameter converter converts between rating systems, the line capacity calculator shows what fits, and the braid to mono converter gives the equivalent mono size.
Roughly 0.44 mm for monofilament, 0.42 mm for fluorocarbon and 0.23 mm for braid. The braid figure varies by brand and strand count, but it is consistently close to half the mono diameter at the same rating.
PE is a Japanese sizing system based on line diameter rather than breaking strain. A useful rule is that diameter in millimeters is roughly 0.165 times the square root of the PE number, so PE 2.0 is about 0.23 mm.
Because reel capacity is quoted by diameter, not by pound test, and diameter varies between brands. If your line is thicker than the manufacturer’s reference line, you will fit less on the spool even at the same strength.
Yes. Thinner line has less air resistance and less friction through the guides, so it casts noticeably further. This is one of the main practical advantages of braid over mono at the same breaking strain.
Slightly, at the same pound test — roughly 0.02 to 0.03 mm thinner in the mid range. The bigger differences are that fluorocarbon sinks, is nearly invisible underwater and is more abrasion-resistant.
Using the nominal diameter table, PE 0.8 is about 0.148 mm, which sits at 8 to 10 lb braid, and PE 1.5 is about 0.205 mm, which sits at 15 to 20 lb braid. Makers vary around these numbers depending on carrier count and coating, so treat them as the center of the range rather than a spec. Every row of the chart above lists its PE equivalent.
Line Diameter Converter · Braid to Mono Converter · Reel Line Capacity Calculator · Line strength chart
Line Diameter Converter · Braid to Mono Converter · Reel Line Capacity Calculator
Charts on the same subject: Fishing Line Strength Chart · Fishing Reel Size Chart · Fishing Swivel Size Chart
Also worth reading: Fly line weight chart
Please note: every figure on this page is an estimate, not a measured result. Tolerances between brands, wear on your gear and your own setup all change the outcome. TackleCalc has no connection to any brand mentioned here, and this content is for reference only.