Fishing Line Size (Go) Converter & Line Capacity Calculator | PE, Nylon & Fluoro lb Conversion, Backing and Leader Size
This tool converts between Japanese line sizes (go), lb (pounds), kg and standard diameter for nylon, fluorocarbon, PE and ester lines, and calculates how many meters of a different size will fit from a spool capacity such as “3-100” or “PE1-200”. Just paste the notation from the spool or catalog to read it, and lb notation (e.g. 8lb-100m) is supported too. When you wind only 150m or 200m of a thin main line, it also shows the backing length you need and the share of backing and main line on the spool. Includes the shock leader size to match your PE (centered on size × 4, with thinner and thicker options), a drag guide calculated from the weaker of main line and leader (in 500ml plastic bottles), and a chart of standard diameter and strength by size.
Convert fishing line size (go), lb and diameter
Choose the line type and enter a size, lb rating or diameter to get the other two plus the strength in kg. Handy when you want to think of an imported lb-rated line in Japanese sizes, or find out roughly how many lb a given size is.
Size (go)
#0.8
Approx. strength
16lb
Standard diameter for size
0.148mm
Other lines of similar strength
Nylon / fluoro
About #4
Standard diameter 0.33mm
Ester
About #3.6
Standard diameter 0.311mm
Nylon and fluorocarbon of the same size are nearly identical in diameter and strength. For the same strength, PE needs only about 1/4–1/5 the size (PE #1 ≈ nylon #5).
Assumptions
- Standard diameters follow the rule “#1 = 0.165mm, size proportional to cross-sectional area”. Nylon, fluoro and ester lines are made to these diameters.
- Strengths in lb and kg are typical conversion values. Always go by the rating on the product package.
- Line capacity assumes the line is wound with no gaps. Actual length varies with winding tension and line stiffness.
Your inputs are only saved in this browser and are never sent to a server.
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About Fishing Line Size (Go) Converter & Line Capacity Calculator | PE, Nylon & Fluoro lb Conversion, Backing and Leader Size
The Fishing Line Size Converter & Line Capacity Calculator converts between Japanese line size (go), lb (pounds), kg and standard diameter for four types of fishing line—nylon, fluorocarbon, PE and ester—and also calculates reel line capacity, backing length, shock leader size and drag settings in one place. Standard diameters follow the rule “#1 = 0.165mm, size proportional to cross-sectional area”, so #3 is 0.285mm and #0.8 is 0.148mm. Strengths use typical conversion values: roughly #1 = 4lb for nylon and fluoro, #1 = about 20lb for PE, and #0.3 = about 1.5lb for ester. Because size is proportional to cross-sectional area, what fits on a spool is determined by “size × length”: for the same material, a spool rated #3-100m holds 150m of #2 or 200m of #1.5. Paste notation from a spool or catalog such as “Nylon (#-m) 2.5-125, 3-100”, “PE #1-200m” or “8lb-100m” and it is read automatically, with lb ratings converted to sizes for the calculation. When you want to wind only 150m of a thin main line, it subtracts the main line volume from the spool capacity and shows the backing length you need and the share of backing and main line on the spool. For PE, it suggests a shock leader using “PE size × 4” as standard, with thinner (×3) and thicker (×5) options in commercially available sizes, and gives a drag setting of 1/4–1/3 of the strength of the weaker of main line and leader, expressed as a number of 500ml or 2L plastic bottles.
How to use Fishing Line Size (Go) Converter & Line Capacity Calculator | PE, Nylon & Fluoro lb Conversion, Backing and Leader Size
- 1In “Size / lb / diameter conversion”, choose the line type and enter a size, lb rating or diameter to see the other values and the sizes of other lines with the same strength
- 2In “Line capacity conversion”, paste the spool notation (e.g. 3-100) or enter the labeled line, size and length
- 3Choose the type and size of line you want to wind, and check the length that fits and the table of lengths by size
- 4To wind a short length of thin line, use “Backing length”: enter the main line size and length and the backing line to see how many meters of backing you need
- 5If you use PE, use “Leader & drag guide” to get the leader size for your PE and how many kg to set the drag to
- 6Use “Copy results” or “Copy URL with these settings” for a shopping note at the tackle shop or to share with fishing friends
Great for
- Find out which nylon, fluoro and PE sizes match an imported lure rod rated “6-12lb”
- Find out roughly how many lb PE #0.8 is and which fluoro size it equals
- Find out how many meters of #2 or #2.5 fit on a reel whose spool says “3-100”
- Decide how much nylon backing to wind when you want only 150m of PE #0.6
- Decide the shock leader size to pair with PE #1
- Find out how many kg to set the drag to, and how to measure it with plastic bottles
- Check how many lb ester line #0.3 for aji (horse mackerel) fishing is, and how its strength compares with the leader
- Note down candidate sizes, lb ratings and lengths before buying line at the tackle shop
Good to know
- Standard diameters are based on the rule “#1 = 0.165mm, size proportional to cross-sectional area”. Nylon, fluoro and ester lines are made to these diameters, but PE size is determined by strength (denier), so its diameter is only a guide.
- Strengths in lb and kg are typical values from commonly used conversion tables. The same size can differ by about ±20% depending on manufacturer, product and PE braid count (4 or 8 strands), so go by the rating on the package.
- Line capacity is calculated assuming the line is wound with no gaps. The length that actually fits varies with winding tension, line stiffness (fluoro is stiffer) and line memory.
- Line capacity conversions between PE and nylon/fluoro are approximate. PE is braided and its cross-section isn’t round, so if the spool lists a PE capacity, use that.
- The leader rule of “PE size × 4” and the drag rule of “1/4–1/3 of line strength” are common guidelines. Adjust them for your target fish, fishing spot and knot.
- Your inputs are saved only in this device’s browser and are never sent to a server.
Questions this tool answers
Use Fishing Line Size (Go) Converter & Line Capacity Calculator | PE, Nylon & Fluoro lb Conversion, Backing and Leader Size for searches like these:
- Find out how many lb PE #0.8 is
- Find out what Japanese size 16lb fluoro is
- Find out how many meters of #2 fit on a reel rated 3-100
- Calculate the backing length for winding 150m of PE
- Find the right leader size for PE #1
- Learn how to measure a drag setting with plastic bottles
- See a chart of fishing line sizes and diameters
- Find out the strength of ester line #0.3
FAQ
- How many lb is PE #0.8?
- The typical value is about 16lb (about 7.3kg). PE strength varies by product even at the same size—8-strand lines are often rated stronger than 4-strand—so the range is roughly 14–18lb. Fluorocarbon of similar strength is about #4; for the same strength, PE needs only about 1/4–1/5 the size.
- How do nylon and fluoro sizes relate to lb?
- Roughly #1 = 4lb, so #2 = 8lb, #3 = 12lb, #4 = 16lb and #5 = 20lb. Thicker lines are a little weaker than proportional: #6 is about 22lb and #8 about 30lb. Nylon and fluorocarbon of the same size are nearly identical in diameter and strength.
- What does a reel line capacity of “3-100” mean?
- It means the spool holds 100m of #3 line. The material and units are usually shown, as in “Nylon (#-m)” or “PE (#-m)”, and some list lb instead (lb-m). Because size is proportional to the line’s cross-sectional area, for the same material you can wind until “size × length” is the same. For 3-100, that’s 150m of #2, 200m of #1.5 or 75m of #4.
- How much backing do I need?
- Subtract the volume of main line you want to wind (size × length) from the spool capacity (size × length), then divide by the size of the backing line. For example, to wind 150m of #1 nylon on a spool rated #3-100m: 300 − 150 = 150, divided by #3 backing gives 50m. Filling slightly below the rim (around 95%) rather than to the very edge reduces tangles.
- What size leader should I use with PE #1?
- A common guideline is “PE size × 4”, so PE #1 pairs with #4 fluorocarbon (about 16lb). Go thinner at #3 (×3) where there are few snags or the fish are finicky, and thicker at #5 (×5) on rough rocky shores or around tetrapods. Leader length is commonly 1–2 hiro (1.5–3m).
- How many kg should I set the drag to?
- A common guideline is 1/4–1/3 of the strength of the weaker of the main line and leader. If you tie #4 fluoro (about 16lb ≈ 7.3kg) to PE #1 (about 20lb ≈ 9kg), the weaker leader is the basis, giving about 1.8–2.4kg. Put water-filled 500ml plastic bottles (about 0.5kg each) in a bag, tie it to the end of the line, raise the rod and lift, and adjust so the line slips out just before the bag lifts.
- How does fishing line size relate to diameter (mm)?
- Standard diameter is “diameter = 0.165mm × √size”: #1 = 0.165mm, #2 = 0.235mm, #3 = 0.285mm, #4 = 0.330mm and #0.8 = 0.148mm. Because size is proportional to cross-sectional area, quadrupling the size doubles the diameter. PE size is set by strength, so its diameter is only a guide.
- How many lb is ester line #0.3?
- About 1.5lb (about 0.7kg) is the guide; #0.2 is about 1lb and #0.4 about 2lb. Ester has little stretch and high sensitivity but is weak against sudden force, so tie on a fluorocarbon leader (around #0.8–1.5) and set the drag light.
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