Tippet 101
Tippet is the part of the leader most beginners get wrong, and the part that decides whether a cast lays out properly. The naming is counterintuitive and the packaging tells you nothing useful, but the working rule fits on a field card.
What tippet is
Your leader is the clear, tapered length of monofilament between the coloured fly line and the fly, thick at one end and thin at the other. The last two feet of the thin end is the tippet, and that is where you tie on the fly. Every fly change cuts it shorter, and once the working end is too thick to tie a small fly to, you splice on fresh tippet material from a spool to rebuild the leader to its original length.
Tippet spools are labelled with an X number, running from 0X (thick) down through 7X or 8X (thin). The scale runs backwards from intuition: a bigger X number means a thinner string. You do not need to memorize the diameters in thousandths of an inch, only that the X numbering is the rule's input.
The divide-by-3-or-4 rule
Take the size of your fly, divide by 3 or 4, and that is your tippet X. A size 16 mayfly imitation divides to 4X or 5X. A size 12 caddis divides to 3X or 4X. A size 8 streamer divides to 2X or 3X. When the math does not land cleanly, round.
| Fly size | Divide by 3 or 4 | Tippet X |
|---|---|---|
| Size 6 | 6 ÷ 3 or 4 | 1X or 2X |
| Size 8 | 8 ÷ 3 or 4 | 2X or 3X |
| Size 12 | 12 ÷ 3 or 4 | 3X or 4X |
| Size 14 | 14 ÷ 3 or 4 | 4X or 5X |
| Size 16 | 16 ÷ 3 or 4 | 4X or 5X |
| Size 18 | 18 ÷ 3 or 4 (round) | 5X or 6X |
| Size 20 | 20 ÷ 3 or 4 (round) | 6X or 7X |
The reason there are two numbers is that the same hook size can carry very different flies. A size 12 hook can be a delicate, high-floating dry or a heavy, weighted nymph, with the same hook number and a very different cast. Use the thinner option for the lighter fly (4X for a size 12 dry) and the thicker option for the heavier or weighted one (3X for a size 12 weighted nymph). Tippet diameter is less about breaking strength than about delivering energy: too thin for the fly's weight, and the cast collapses before the fly turns over, piling in a heap. Too thick for a small fly, and the fly slams the water instead of landing softly, which trout in clear water see.
When to break the rule
The divide-by-3-or-4 rule covers most days on most water. A few situations push you off it.
Bigger or stronger fish. Size up one X for muscle in the fight. A size 14 fly normally drifts on 5X, but a river full of strong fish gets 4X.
Fast, broken water. Riffles and pocket water hide the leader, so use the thicker option. The trout will not inspect it.
Slow, clear water with picky fish. On tailwaters, spring creeks, or sight-fishing in flat pools, step one X finer than the rule suggests. A size 16 the math calls 4X might need 6X to fool a fish that has been seeing flies all season.
Weighted streamers. Heavy, articulated, or bead-headed streamers need thicker tippet than the math suggests, because the fly needs muscle behind it to turn over. A size 8 streamer with a tungsten head fishes better on 1X or even 0X than on 2X.
What to actually buy
For a trout angler running the Every Day Trout Box, three spools cover almost everything: 2X handles streamers and heavy nymphs, 4X handles most dries and standard nymphs, and 6X handles small dries and picky fish. Spools come in standard 30-metre lengths and last a long time, so keep them banded together in your kit. If you fish a wider range of fly sizes, add 3X and 5X to bridge the gaps. Ignore the pound-test rating on the package: it tells you when the line breaks, which is the wrong question. The X number tells you whether the cast will work, and the cast working is the question that actually matters.
Tippet is cheap insurance
A spool of tippet costs around the price of a coffee. The divide-by-3-or-4 rule is the smallest, cheapest piece of fly fishing knowledge that protects all the others.