Hook size
Also called Fly hook size, Hook sizing
Hook size is the numbering system that tells you how big a fishing hook is. For most trout hooks, bigger numbers mean smaller hooks, and hooks larger than size 1 use “aught” sizes (1/0, 2/0, 3/0).
- Group
- Hooks
- Category
- Fly tying — materials & tools
- Level
- Beginner
- Water
- Fresh & salt
Last updated
What Hook size means
Most fly hooks are labeled by size, like 18, 14, 8, 2, then 1/0, 2/0, 3/0. In the common trout-style range, a size 18 is smaller than a size 12. Once you get to “aught” sizes, the numbers go the other direction, 2/0 is larger than 1/0.
Hook size is about the hook’s overall dimensions, especially the gap. It is not a single measurement, because different hook models can run a little long, short, wide, or narrow even when the printed size matches.
Tiers and anglers use hook size to match a fly to the food and to the job. A Zebra Midge might be tied on a small hook, a Pheasant Tail Nymph on a mid-size hook, and a Woolly Bugger or Clouser Minnow on a larger hook. The same pattern name can be tied in several sizes.
Why it matters on the water
Hook size drives more than “how big the fly looks.” It affects how the fly floats or sinks, how much weight a bead adds, and how the fly rides in the current. If a nymph keeps snagging, moving to a smaller hook or a different hook style can change the sink rate and the way it tracks.
Hook size also sets the ceiling for tippet choice and knots. A tiny hook eye can be hard to thread with thicker tippet, and some knots seat cleaner on larger eyes. Knowing the size lets you pick a tippet that fits the eye and matches the fly’s scale without guessing.
Read next
- Dry flyA dry fly is a floating fly meant to be fished on the surface, where you can see it and the take.
- NymphA nymph is a subsurface fly meant to imitate an aquatic insect in its immature stage, or a small food item drifting in the current. Nymphs are fished with or without weight, an indicator, or tight-line methods.
- StreamerA streamer is a fly meant to be moved to imitate a baitfish, leech, sculpin, or crayfish. It is often fished with strips, swings, or a steady retrieve, but it can also be dead-drifted.
- TippetTippet is the thin, level line tied to the end of your leader. It’s the section you cut back and replace as you change flies and re-tie knots.