ThinkVault ToolsFishing Line Gou-to-lb Converter, Sinker Weight & Tidal Bite Calculator

Angling, Lure & Saltwater Utility

Fishing Line Gou-to-lb Converter, Sinker Weight & Tidal Bite Calculator

Fishing line material

Japanese Gou number (#)

Results

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Practical knot breaking strength

9.6 kg

Straight test: 25 lb (11.3 kg) · Ø 0.205 mm

Standard diameter (mm)0.205 mm
Recommended fluorocarbon leader (#)#3.8
Sinker weight (grams / oz)11.25 g (0.4 oz)
Recommended sinker for depth~36 g
Lunar phase & tidal currentLunar day 10 · Moderate tide (steady tidal flow)

Lunar day uses Hong Kong Observatory 2025–2028 conversion tables (Hong Kong civil dates). Tide categories are approximate; consult local tide tables.

Practical knot breaking strength

9.6 kg (25 lb)

Method and common questions

Tax, lending, holiday and protection rules vary by place and date. Check current local rules and provider terms. Results are estimates.

Understanding Japanese Line Gou (#) vs. Pound Test (lb)

Japanese fishing lines (JAFTMA standard) are rated by Gou (#), which measures physical line diameter rather than breaking strength. A #1.5 braided PE line (0.205 mm diameter) tests around 25 lb straight pull, whereas a #1.5 fluorocarbon line of the exact same diameter tests around 6 lb.

Factoring in knot efficiency (around 85% for an FG knot or 70% for an Albright/Uni knot) prevents unexpected main-line breaks when setting reel drag.

  • 1 Gou (1 Monme) sinker equals exactly 3.75 grams (0.132 oz).
  • Lunar day uses Hong Kong Observatory 2025–2028 conversion tables (Hong Kong civil dates). Tide categories are approximate; consult local tide tables.

Matching Sinker Weight to Water Depth

In moderate coastal currents, a practical rule of thumb for bottom and boat fishing is roughly 15g–20g (4–5 Gou) of sinker weight per 10 meters of water depth.

Method

Standard Japanese line diameter (mm) = 0.165 × √Gou. Practical Knot Strength (kg) = Straight Test (lb) × 0.453592 × Knot Retention %. Sinker Weight (g) = Sinker Gou × 3.75. Lunar day uses Hong Kong Observatory 2025–2028 conversion tables (Hong Kong civil dates). Tide categories are approximate; consult local tide tables.

Last checked: 2026-10-25

Hong Kong Observatory conversion tables

FAQ

What size fluorocarbon leader should I pair with braided PE line?
A balanced all-around ratio for lure and boat fishing is 2x to 2.5x the PE Gou number (for example, #1.5 PE paired with #3.0 to #4.0 fluorocarbon leader).
How many grams is a #3 sinker?
Under the standard 3.75g per Gou scale, a #3 sinker weighs 11.25 grams (approx. 0.4 oz), and a #8 sinker weighs 30 grams.
Are Spring Tides or Neap Tides better for fishing?
Spring tides (around the new and full moon) create strong tidal movement that triggers active feeding during the 2-hour window around slack tide, while Moderate tides offer steadier bottom contact in deep water.
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