Reference guide
Fishing Line Size Chart
Line is sold by pound test, but diameter is what determines how much fits on a spool and how the line handles. On the typical diameters below, 10 lb braid is about as thick as 4 lb mono or thinner, and 30 lb braid is about as thick as 10 lb mono. Those are diameter comparisons, not equal-strength replacements. Check the actual product and spool specifications before filling a reel.
That is why you cannot compare line types by the number on the box: 10 lb of one is not the same line as 10 lb of another.
Line diameter by pound test
Same pound test, very different thickness. That is the whole reason this page exists.
10 lb test
20 lb test
30 lb test
Every pound test, in inches with millimeters underneath. The ranges are wide because diameter at a given test varies between brands, and between products within a brand.
Scroll the table sideways to see every column.
| Pound test | Monofilament | Fluorocarbon | Braided line | Notes |
|---|---|---|---|---|
| 4 lb | .007"–.009"0.18–0.23 mm | .006"–.008"0.15–0.20 mm | — | |
| 6 lb | .008"–.010"0.20–0.25 mm | .008"–.010"0.20–0.25 mm | — | |
| 8 lb | .009"–.011"0.23–0.28 mm | .009"–.011"0.23–0.28 mm | — | |
| 10 lb | .010"–.013"0.25–0.33 mm | .010"–.013"0.25–0.33 mm | .005"–.008"0.13–0.20 mm | Braided line: about the diameter of 4 lb mono or thinner |
| 12 lb | .012"–.014"0.30–0.36 mm | .011"–.014"0.28–0.36 mm | — | |
| 15 lb | .014"–.016"0.36–0.41 mm | .013"–.016"0.33–0.41 mm | .007"–.009"0.18–0.23 mm | Braided line: about the diameter of 4 lb mono |
| 20 lb | .017"–.020"0.43–0.51 mm | .016"–.019"0.41–0.48 mm | .008"–.010"0.20–0.25 mm | Braided line: about the diameter of 6 lb mono |
| 25 lb | .019"–.022"0.48–0.56 mm | .017"–.022"0.43–0.56 mm | — | |
| 30 lb | .021"–.024"0.53–0.61 mm | .021"–.024"0.53–0.61 mm | .010"–.012"0.25–0.30 mm | Braided line: about the diameter of 10 lb mono |
| 40 lb | .024"–.028"0.61–0.71 mm | .024"–.028"0.61–0.71 mm | .012"–.014"0.30–0.36 mm | Braided line: about the diameter of 12 lb mono |
| 50 lb | .027"–.032"0.69–0.81 mm | .027"–.031"0.69–0.79 mm | .013"–.016"0.33–0.41 mm | Braided line: about the diameter of 15 lb mono |
| 60 lb | .030"–.035"0.76–0.89 mm | .030"–.035"0.76–0.89 mm | — | |
| 65 lb | — | — | .015"–.018"0.38–0.46 mm | Braided line: about the diameter of 15 lb mono |
| 80 lb | .034"–.040"0.86–1.02 mm | .035"–.040"0.89–1.02 mm | .017"–.020"0.43–0.51 mm | Braided line: about the diameter of 20 lb mono |
| 100 lb | — | — | .019"–.023"0.48–0.58 mm | Braided line: about the diameter of 25 lb mono |
A dash means that pound test is not commonly sold in that line type. Diameters are typical published figures, not a specification: check the spool. Millimeters are converted at 25.4 mm to the inch and rounded to two decimals.
Sources for this guidance
- Sufix Elite monofilament specifications Published pound-test and diameter pairs for one monofilament product family, for example 4 lb at 0.008 in., 10 lb at 0.012 in. and 30 lb at 0.022 in.
- Sufix 832 Advanced Superline specifications Published pound-test and diameter pairs for one braided-line product family, for example 10 lb at 0.008 in., 20 lb at 0.009 in. and 30 lb at 0.011 in.
- Seaguar TactX braid specifications A second braid with published diameters, for example 20 lb at 0.010 in. and 30 lb at 0.011 in., showing why the actual product diameter matters more than a universal ratio.
- Seaguar InvizX fluorocarbon: pound tests and diameters The product page's pound-test options list 4, 6, 8, 10, 12, 15, 20 and 25 lb InvizX at 0.006, 0.008, 0.009, 0.010, 0.011, 0.013, 0.016 and 0.017 in. respectively. Each figure is the lower end of the chart's fluorocarbon range for that pound test.
- Orvis tippet chart: diameters and breaking strengths Diameters and approximate breaking strengths for Orvis Super Strong nylon tippet, from 8X at 0.003 in. and 1.75 lb to 0X at 0.011 in. and 15.5 lb. The strength listed for each X size falls inside the tippet table's range for that size.
How to use this chart
- Start with the equipment. Read the line range printed on the rod and the capacity printed on the reel spool. Those limits narrow the useful choices before species or water clarity enter the decision.
- Compare diameter when changing materials. If a spool lists capacity for 10 lb mono, compare that row with 30 lb braid: their typical diameter ranges overlap, even though their pound-test labels do not. It is a starting comparison of diameter, not of yards: where the spool also lists a braid capacity, use that figure.
- Then adjust for the fishing. Cover and abrasion may justify heavier line; clear, open water may let you go lighter. Check the actual product diameter before filling the spool because brand specifications vary.
Metric line sizes
Many spools print diameter in millimeters. Find the size on your spool, then read which pound tests list that diameter in their typical range in the chart above. Most sizes match more than one test, because the ranges overlap and makers rate line differently.
Scroll the table sideways to see every column.
| Diameter | Monofilament | Fluorocarbon | Braided line |
|---|---|---|---|
| 0.10 mm | Thinner than 4 lb | Thinner than 4 lb | Thinner than 10 lb |
| 0.12 mm | Thinner than 4 lb | Thinner than 4 lb | Thinner than 10 lb |
| 0.15 mm | Thinner than 4 lb | 4 lb | 10 lb |
| 0.18 mm | 4 lb | 4 lb | 10–15 lb |
| 0.20 mm | 4–6 lb | 4–6 lb | 10–20 lb |
| 0.22 mm | 4–6 lb | 6 lb | 15–20 lb |
| 0.25 mm | 6–10 lb | 6–10 lb | 20–30 lb |
| 0.28 mm | 8–10 lb | 8–12 lb | 30 lb |
| 0.30 mm | 10–12 lb | 10–12 lb | 30–40 lb |
| 0.35 mm | 12 lb | 12–15 lb | 40–50 lb |
| 0.40 mm | 15 lb | 15 lb | 50–65 lb |
| 0.45 mm | 20 lb | 20–25 lb | 65–80 lb |
| 0.50 mm | 20–25 lb | 25 lb | 80–100 lb |
| 0.55 mm | 25–30 lb | 25–30 lb | 100 lb |
| 0.60 mm | 30 lb | 30 lb | Thicker than 100 lb |
Each size is matched against the millimeter ranges as the chart above prints them, and a range counts both of its ends. A product rated outside these tests is not wrong: check its own label.
Braid and mono of about the same diameter
These pairs match diameter, which decides how much line fits on a spool, not strength: 30 lb braid is still sold as 30 lb line, while the 10 lb mono it matches is sold as 10 lb.
Each pair puts the middle of a braid row's typical range against the monofilament row whose middle is closest, the same comparison the Line Selector quotes and the Notes column in the chart shows. In the first table, braid thinner than the lightest mono in the chart reads "or thinner".
Read the second table when a reel lists its capacity in mono and you plan to fill it with braid. On paper, a spool's yards fall with the square of the line's diameter, and on the middle of each typical range that arithmetic puts the braid a row gives as its match within 10 percent of the mono's yards either way. It puts a braid marked thinner above that and one marked thicker below it, and where the mono falls between two braid rows, the lighter braid above the mono's yards and the heavier below. Makers' own figures for the matches come out lower: the 8 spinning reels on the reel size chart that list both a mono test and its match here are rated for 61 to 93 percent as many yards of the braid as of the mono. Check both spools, because brands differ.
| Braid | Closest mono |
|---|---|
| 10 lb | 4 lb mono or thinner |
| 15 lb | 4 lb mono |
| 20 lb | 6 lb mono |
| 30 lb | 10 lb mono |
| 40 lb | 12 lb mono |
| 50 lb | 15 lb mono |
| 65 lb | 15 lb mono |
| 80 lb | 20 lb mono |
| 100 lb | 25 lb mono |
| Mono | Closest braid |
|---|---|
| 4 lb | 15 lb braid (10 lb braid is thinner) |
| 6 lb | 20 lb braid |
| 8 lb | Between 20 and 30 lb braid |
| 10 lb | 30 lb braid |
| 12 lb | 40 lb braid |
| 15 lb | 50 lb braid (65 lb braid is thicker) |
| 20 lb | 80 lb braid |
| 25 lb | 100 lb braid |
Choosing between mono, fluorocarbon and braid
Monofilament
A single extruded nylon strand. The cheapest, most forgiving line and still the right answer more often than its reputation suggests.
Stretch: High (roughly 15-30%) · Visibility: Moderate underwater · Abrasion: Moderate · In water: Floats or sinks very slowly
Where it wins: Stretch cushions hooksets and head shakes, which keeps treble-hook baits pinned and light-wire hooks from tearing out. Ties easily, handles well on cheap reels, and is the most affordable line by a wide margin.
What it costs you: Stretch costs you bite detection at depth or distance. It absorbs water, weakens with UV exposure, and takes a set on the spool, so it needs replacing more often than braid.
Fluorocarbon
A dense polymer with a refractive index close to water, which makes it harder for fish to pick out.
Stretch: Low to moderate · Visibility: Low underwater · Abrasion: High · In water: Sinks
Where it wins: Low visibility in clear water, good abrasion resistance against rock and shell, and it sinks, which helps get crankbaits and bottom baits down.
What it costs you: Stiffer than mono, so it can be fussy in light tests and on small spinning spools. Costs more. Knots need to be seated slowly and wet or the line will fail at the knot.
Braided line
Multiple fibers woven into a rope. Very thin for its strength and effectively no stretch.
Stretch: Almost none · Visibility: High underwater · Abrasion: High against grass, lower against sharp rock and shell · In water: Floats
Where it wins: Thin diameter means more line on the spool and better casting distance. No stretch gives you direct bite detection and hard hooksets at long range or in deep water. Lasts several seasons.
What it costs you: Highly visible, so it usually wants a leader in clear water. No stretch means a stiff rod and braid together will pull hooks out of soft-mouthed fish. Costs the most per spool and needs specific knots.
How to pick a pound test
- Start from the cover, not the fish. Most break-offs happen against wood, rock, shell or grass rather than from a fish pulling hard. Open water lets you fish lighter than the same species in timber.
- Check the rod. Rods carry a printed line rating. Fishing far above it risks the blank; fishing far below it means the rod will not load properly on the cast.
- Check the reel's capacity. An under-filled spool casts badly. Match diameter to what the spool is designed to hold; the Fishing Reel Size Chart explains how reel size classes relate to capacity.
- Clear water pushes you lighter. Line diameter is one of the few variables a fish can actually see. Dropping a size often produces more bites than changing lures.
Leader and tippet sizes
Ready to join your lines or tie on a hook? Use the Fishing Knot Finder for a practical connection and tying steps.
Leaders on spinning and casting tackle
Each row is the Line Selector's answer for an intermediate angler with the inputs shown under the situation, and the knot is the one the Knot Finder picks for that join, with its alternative underneath. Where the knot is cast through the guides, the Knot Finder was asked for a slim connection, and no bulkier alternative is shown. Not every setup needs a leader: fluorocarbon main line is already leader material.
Scroll the table sideways to see every column.
| Situation | Main line | Leader | Join |
|---|---|---|---|
| Finesse bass on spinning tackleBass · Plastic worm · Spinning | 10–15 lb braided line | 8–12 lb fluorocarbon | Double Uni Knotor FG Knot |
| Bass on a baitcaster around coverBass · Plastic worm · Baitcasting | 12–17 lb fluorocarbon | No leader | Uni Knot, straight to the baitor Improved Clinch Knot |
| Walleye jiggingWalleye · Jigging | 8–10 lb braided line | 8–10 lb fluorocarbon | Double Uni Knotor FG Knot |
| Trout on spinning tackle in clear waterTrout · Spinning | 4–6 lb monofilament | 4–6 lb fluorocarbon | Double Uni Knotor Double Surgeon's Knot |
| Inshore redfish around oyster shellRedfish · Spinning · Saltwater | 15–30 lb braided line | 20–30 lb fluorocarbon | FG KnotA slim connection |
| Surf casting with heavy sinkers (striped bass)Striped Bass · Surf fishing · Saltwater | 30–50 lb braided line | 50–60 lb monofilament | FG KnotA slim connection |
| Northern pikeNorthern Pike · Spinning | 30–50 lb braided line | 20–40 lb wire, or heavier fluorocarbon | Palomar Knot to the leader's swivelor Uni Knot |
Pound tests are ranges because the right test depends on the cover and the fish; brands also rate line differently.
- Lighter or heavier than the main line. A leader lighter than the main line is usually the part that breaks on a snag, so you lose the leader and the lure rather than a long length of braid. A heavier one is there for abrasion, teeth or casting load: oyster shell and rock, pike, and in the surf the force of the cast itself.
- Short or long. A short leader keeps the knot out of the rod guides when you cast. A longer one keeps more of the visible braid away from the fish and leaves more to cut back after abrasion, but the knot then passes through the guides on every cast, which is where a slim knot such as the FG helps. A surf shock leader is long by design: it has to reach back onto the reel spool so that it, not the thin braid, takes the force of the cast.
- Wire. Ready-made wire leaders usually come with a swivel, so the knot listed for pike is the Knot Finder's knot for tying braid to a swivel.
Fly leaders and tippet
Fly leaders and tippet use X sizes, which describe diameter rather than strength. The rule is straightforward: diameter in thousandths of an inch equals 11 minus the X number, so 5X is .006 inches. Breaking strength at a given X still varies by material and brand.
Scroll the table sideways to see every column.
| Size | Diameter | Typical strength | Typically used for |
|---|---|---|---|
| .015 | 0.015"0.38 mm | 25 lb | The heaviest pairing on the Orvis chart for 2/0 to 5/0 flies. |
| .013 | 0.013"0.33 mm | 20 lb | Large flies from 2/0 to 5/0. |
| .012 | 0.012"0.30 mm | 18.5 lb | The lightest pairing on the Orvis chart for 2/0 to 5/0 flies. |
| 0X | 0.011"0.28 mm | 13–16 lb | Bass bugs and large streamers in sizes 4 to 1/0. |
| 1X | 0.010"0.25 mm | 11–14 lb | Large streamers and bass flies. |
| 2X | 0.009"0.23 mm | 9–12 lb | Streamers and heavy nymph rigs. |
| 3X | 0.008"0.20 mm | 7–9 lb | Large nymphs, small streamers, big dries. |
| 4X | 0.007"0.18 mm | 5–7 lb | General trout nymphing and larger dry flies. |
| 5X | 0.006"0.15 mm | 4–5.5 lb | The default trout tippet for most dry-fly and nymph work. |
| 6X | 0.005"0.13 mm | 3–4 lb | Small dries and clear, low water. |
| 7X | 0.004"0.10 mm | 2–3 lb | Midges and heavily pressured trout. |
| 8X | 0.003"0.08 mm | 1–2 lb | The finest normal tippet; midge fishing in flat water. |
Want a specific answer?
The Line Selector gives you a line type, a pound test and whether this setup needs a leader.
Related guides
- Fishing Hook Size ChartSelected common sizes from #28 to 12/0 with typical uses, and why the same number differs between brands.
- Fishing Reel Size ChartSpinning, baitcasting, conventional and fly reel classes with typical line capacity and what each size is for.
- Fishing Rod Size GuideWhat length, power and action each control, and how to read the specs printed on a blank.
- Split Shot and Sinker Size ChartUK split shot sizes in grams, the separate US size names, and published weights for common sinker shapes.