Fishing Line Converter: Pound Test to Diameter (Mono & Braid)
Convert fishing line pound test to diameter in inches and millimeters, and compare monofilament against braided line for the same strength.
Select a line type and pound test to see diameter, or enter a diameter to find the matching pound test.
30 lb braid ≈ same diameter as 8 lb mono
50 lb braid ≈ same diameter as 12 lb mono
Understanding Fishing Line Measurements
Fishing line is rated by its breaking strength (pound test) and its physical diameter. The relationship between these two measurements differs significantly between monofilament (mono) and braided line, which is why anglers need to understand both specifications when selecting line for their reel and target species.
Pound Test (Breaking Strength):
Pound test indicates the minimum force required to break the line. A 10 lb test line will hold at least 10 pounds of straight-pull force before breaking. However, knots, abrasion, UV exposure, and age all reduce the actual breaking strength below the rated value.
Monofilament Diameter Reference:
Monofilament fishing line has a relatively consistent relationship between pound test and diameter:
| Pound Test | Diameter (inches) | Diameter (mm) | Typical Use |
|---|---|---|---|
| 2 lb | 0.005 | 0.13 | Ultra-light, ice fishing |
| 4 lb | 0.007 | 0.18 | Panfish, trout |
| 6 lb | 0.009 | 0.23 | Trout, bass (light) |
| 8 lb | 0.010 | 0.25 | Bass, walleye |
| 10 lb | 0.012 | 0.30 | General freshwater |
| 12 lb | 0.013 | 0.33 | Bass, pike |
| 15 lb | 0.015 | 0.38 | Large freshwater |
| 17 lb | 0.016 | 0.41 | Inshore saltwater |
| 20 lb | 0.018 | 0.46 | Saltwater, catfish |
| 25 lb | 0.020 | 0.51 | Heavy saltwater |
| 30 lb | 0.022 | 0.56 | Big game fishing |
| 50 lb | 0.028 | 0.71 | Offshore, big game |
| 80 lb | 0.035 | 0.89 | Heavy big game |
Braided Line Comparison:
Braided line is significantly thinner than monofilament at the same pound test. This is its primary advantage, as thinner line casts farther, sinks faster, and allows more line on the reel.
| Braid Pound Test | Braid Diameter (in) | Mono Equivalent Diameter | Mono Equivalent Strength |
|---|---|---|---|
| 10 lb braid | 0.005 | 0.005 | 2 lb mono |
| 20 lb braid | 0.008 | 0.008 | 4-6 lb mono |
| 30 lb braid | 0.010 | 0.010 | 8 lb mono |
| 50 lb braid | 0.013 | 0.013 | 12 lb mono |
| 65 lb braid | 0.015 | 0.015 | 15 lb mono |
| 80 lb braid | 0.018 | 0.018 | 20 lb mono |
Conversion Formulas:
Diameter (mm) = Diameter (inches) × 25.4Diameter (inches) = Diameter (mm) / 25.4- Monofilament approximate:
Diameter (inches) ≈ 0.001 × pound test^0.5 + 0.003
Practical Examples:
- Spooling a spinning reel rated for 8-12 lb mono line, you could use 30 lb braid instead (same diameter as 8-10 lb mono), gaining much higher strength with the same reel capacity.
- For bass fishing, 12 lb monofilament (0.013" diameter) casts well on baitcasting reels. The braided equivalent at 0.013" diameter is 50 lb test.
- A reel that holds 200 yards of 10 lb mono will hold approximately 200 yards of 30 lb braid, since both have roughly 0.012" diameter.
Tips:
- Match line diameter to your reel, not just pound test. Reel manufacturers specify line capacity by both pound test and diameter.
- Fluorocarbon line has the same diameter-to-strength ratio as monofilament but is nearly invisible underwater due to its refractive index.
- Braided line has near-zero stretch, providing excellent sensitivity but less shock absorption than mono.
- Replace monofilament line at least once per year, as UV light and moisture degrade its strength over time.
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