What size tippet should I use for what size fly?
Short answer
Divide the hook size by three and round to the nearest X. A size 16 fly takes 5X, a size 20 takes 6X or 7X. Go one size finer on flat, clear water and one size heavier when you are fishing weight, streamers, or anywhere a fish can reach cover.
What size tippet for what size fly?
This is the whole answer, and most days you will not need to think past it.
| Tippet | Diameter | Hook sizes | Typical use |
|---|---|---|---|
| 0X | 0.011in | #1/0–#2 | Big streamers, bass, pike |
| 1X | 0.010in | #4–#8 | Large streamers, big foam dries |
| 2X | 0.009in | #6–#10 | Streamers, large stonefly nymphs |
| 3X | 0.008in | #8–#14 | Weighted nymph rigs, hoppers |
| 4X | 0.007in | #12–#16 | General nymphing, larger dries |
| 5X | 0.006in | #14–#18 | The all-round trout default |
| 6X | 0.005in | #16–#22 | Small dries, clear water, wary fish |
| 7X | 0.004in | #18–#24 | Midges, flat water, spring creeks |
If you carry three spools, carry 4X, 5X and 6X. That covers the overwhelming majority of trout fishing in North America.
How does the rule of 3 actually work?
Divide the hook size by three and round to the nearest whole number. That number is your X size.
| Fly size | Divided by 3 | Tippet |
|---|---|---|
| #12 | 4 | 4X |
| #15 | 5 | 5X |
| #16 | 5.3 → 5 | 5X |
| #18 | 6 | 6X |
| #22 | 7.3 → 7 | 7X |
It is arithmetic, not physics, and it is approximate on purpose. What it gets right is the relationship: as flies get smaller, tippet must get finer, or the fly stops behaving like an insect.
Why does the X number run backwards?
X is a diameter scale inherited from the days when silkworm gut was drawn through a die — each pass through a finer hole earned another X. Higher X means thinner.
The conversion is a subtraction: diameter in thousandths of an inch equals 11 minus the X number. So 5X is 0.006in, 2X is 0.009in, and 7X is 0.004in.
When should you break the rule?
The rule of 3 assumes an average day. Conditions move you a size in one direction or the other, and knowing which direction is most of the skill.
| Situation | Adjust | Why |
|---|---|---|
| Flat, clear, slow water | One size finer | Fish get a long look; thick tippet is visible and stiffens the drift |
| Heavily fished water | One size finer | Educated fish refuse anything that drifts unnaturally |
| Fishing split shot or a heavy point fly | One size heavier | Weight puts shock load on the knot |
| Streamers | Two or three sizes heavier | Takes are violent and the fly is large |
| Fish holding near timber or weed | One size heavier | You need to turn a fish before it reaches cover |
| Wind | One size heavier | Fine tippet will not turn a fly over into a headwind |
A useful test: if you are getting refusals from fish that clearly saw the fly, go finer. If you are breaking off or landing in a pile, go heavier.
Does the fly type change the answer?
It changes it more than the hook size does, in some cases.
- Small dries and midges — go by the rule or finer. A Trico on 4X will not drift correctly no matter how well you cast.
- Big foam attractors — go heavier than the rule suggests. A Chubby Chernobyl is wind-resistant and often carries a dropper; 3X or 4X turns it over where 5X collapses.
- Weighted nymphs — heavier than the rule. A Zebra Midge is tiny, but if it is trailing behind a tungsten anchor fly, the tippet is carrying that weight too.
- General dries — the rule works as written. An Adams in #14 on 5X is about as standard as trout fishing gets.
Monofilament or fluorocarbon?
| Nylon monofilament | Fluorocarbon | |
|---|---|---|
| Buoyancy | Floats — better for dries | Sinks — better subsurface |
| Visibility in water | Slightly more visible | Refracts closer to water |
| Abrasion resistance | Lower | Higher |
| Knot forgiveness | More forgiving | Needs care and lubrication |
| Cost | Lower | Higher |
| Best for | Dry flies, general use | Nymphs, streamers, rocky water |
Frequently asked questions
What is the rule of 3 in fly fishing?
Divide the hook size by three and round to the nearest X size. A size 12 fly takes 4X, a size 18 takes 6X. It is a starting point, not a law — conditions move you a size either way.
Does a higher X number mean thicker or thinner tippet?
Thinner. X is a diameter scale that runs backwards: 7X is finer than 0X. Diameter in thousandths of an inch equals 11 minus the X number, so 5X is 0.006in and 0X is 0.011in.
What happens if my tippet is too heavy for the fly?
A small fly on heavy tippet will not drift naturally — the stiff, thick material drags it and holds it unnaturally straight. On flat water that produces refusals from fish that would otherwise have eaten it.
What happens if my tippet is too light?
You break off fish, and you struggle to turn the fly over on the cast. Fine tippet on a big or wind-resistant fly collapses in a pile instead of straightening, which ruins the presentation before drag ever gets a chance to.
Sources
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