Fly Fishing Leader Calculator
Work out a leader length and taper that suits the water, the fly and the conditions in front of you.
Open tool : Fly Fishing Leader CalculatorTippet Size Calculator
Match tippet size, diameter and typical breaking strength to the fly you are about to tie on.
How to use it
- Start with the flyPick the hook size you are about to tie on. That sets the baseline using the rule of three.
- Adjust for the waterClear low water pushes you finer. Off colour or fast broken water lets you fish heavier without spooking fish.
- Adjust for the fishBigger fish and heavier current mean a heavier tippet so you can land them quickly.
- Check the spoolUse the strength printed on the tippet you actually own. Diameter is standardised, strength is not.
What the X system actually measures
The X rating is a diameter scale, not a strength scale. It is defined by subtracting thousandths of an inch from eleven thousandths: 0X is 0.011 inch, 4X is 0.007 inch, 7X is 0.004 inch. That part is exact and identical across every brand.
Breaking strength is not standardised. Two spools of 5X from different makers can be the same diameter and test several pounds apart depending on the material and how it was drawn. The strengths shown here are typical ranges for nylon, and fluorocarbon of the same diameter usually tests a little differently again. The number printed on your spool wins.
| X size | Diameter | Typical strength | Common use |
|---|---|---|---|
| 0X | 0.011 in | about 15 lb | Large streamers, bass, saltwater leaders |
| 1X | 0.010 in | about 13 lb | Big streamers, heavy nymph rigs |
| 2X | 0.009 in | about 11 lb | Streamers, large dries, hopper rigs |
| 3X | 0.008 in | about 8 lb | Big dries, weighted nymphs |
| 4X | 0.007 in | about 6 lb | General trout dries and nymphs |
| 5X | 0.006 in | about 5 lb | The most common all round trout tippet |
| 6X | 0.005 in | about 3.5 lb | Small dries, clear water, spooky fish |
| 7X | 0.004 in | about 2.5 lb | Tricos, midges, flat clear water |
| 8X | 0.003 in | about 1.75 lb | The smallest midges, spring creeks |
Common questions
What is the rule of three
Divide the hook size by three and you get a starting X size for tippet. A size 18 fly divides to roughly 6X. It is a starting point that has held up for decades, not a rule. Fish size, current speed and how spooky the water is all move it.
Why do tippet strengths differ between brands
The X number describes diameter, not strength. Two spools of 5X can be the same diameter and still test differently depending on the material and how it was drawn. Always read the strength printed on the spool you actually own rather than a generic chart.
Should I go heavier or lighter than the chart says
Heavier when the fish are large, the current is fast, or you are fishing near timber and want to land fish quickly. Lighter when the water is low and clear and the fish are refusing. Going too light and breaking fish off is worse for the fish than being slightly overgunned.