Fly Fishing Tippet Size Calculator
Match tippet X-size to fly hook size and breaking strength.
The rule of 3 and rule of 4 explained.
Essential for fly fishing leader selection.
In fly fishing, the tippet is the fine end of the leader that connects to the fly. Tippet sizes use an X-rating system — higher X numbers mean thinner, weaker tippet.
X-rating to diameter: Diameter (inches) = (11 - X) × 0.001
- 0X = 0.011" (11.5 lb test)
- 2X = 0.009" (8.5 lb test)
- 4X = 0.007" (6 lb test)
- 5X = 0.006" (4.75 lb test)
- 6X = 0.005" (3.5 lb test)
- 7X = 0.004" (2.5 lb test)
Rule of 3: Divide the fly hook size by 3 to get the recommended X-rating. For a size 12 fly: 12/3 = 4X tippet. For a size 18 dry fly: 18/3 = 6X.
Rule of 4: Divide the fly hook size by 4 for a slightly heavier tippet (better turnover, less finesse).
Choosing tippet strength vs. finesse:
- Bigger flies (streamers, nymphs): heavier tippet for casting and fighting fish
- Tiny dry flies: fine tippet for natural drift and presentation
- Spooky fish in clear water: go finer
- Strong currents or large fish: go heavier
Fluorocarbon tippet is less visible underwater and sinks faster (good for nymphs). Monofilament floats better (better for dry flies) and is more supple.