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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.