How hooks are sized, and what the numbers mean
Explainer · Last reviewed 2026-08-14
Hook numbering runs in two directions from a point in the middle, and it is not standardised between manufacturers. Understanding both facts is what stops somebody buying a hook ten times the size they wanted.
THE NUMBERING RUNS BOTH WAYS FROM A MIDDLE. Above the middle, sizes are plain numbers and they get SMALLER as the number gets BIGGER: a size 20 is tiny, a size 10 is small, a size 2 is a decent hook. Below the middle, sizes carry a slash-nought and they get BIGGER as the number gets bigger: 1/0 is the next size up from 1, then 2/0, 4/0, 8/0 and onward into hooks used for large sea fish.
So the sequence from smallest to largest runs: 24, 20, 16, 12, 8, 4, 2, 1, 1/0, 2/0, 4/0, 8/0. The pivot between the two conventions falls between 1 and 1/0, and that is the single most common place for somebody to order a hook of entirely the wrong size.
THERE IS NO ENFORCED STANDARD. Size refers loosely to the gape — the distance between point and shank — but each manufacturer applies it to its own pattern range. A size 4 in one pattern can be visibly different from a size 4 in another, and comparing across brands by number alone does not work. The practical response is to judge hooks by eye against something known, and to treat the number as a rough position in a range rather than a measurement.
WHAT THE SIZE ACTUALLY HAS TO SUIT is the BAIT first and the fish second. A hook has to be large enough that the point is not masked by the bait and small enough that the bait looks like itself. A hook chosen for the fish and not the bait is the commonest source of missed bites in beginner fishing.
AND SIZE IS NOT THE ONLY NUMBER ON THE PACKET. Wire gauge — fine, standard, forged — decides whether the hook will straighten under load or cut through a soft mouth. Shank length changes how the bait sits and how easily the hook can be removed. Pattern decides where the fish is hooked. A size is a starting point and the rest of the specification is what actually does the work.
WHY THIS IS A WELFARE QUESTION AND NOT ONLY A TACKLE ONE: hook size and pattern bear on where a fish is hooked and how easily the hook comes out, and hooking location is the strongest single predictor of whether a released fish survives. Choosing a hook is a decision about the fish's outcome as well as your own.
Why hooking location matters more than any other choice here
Across recreational fisheries, the single strongest predictor of whether a released fish survives is where it was hooked. Fish hooked in the jaw or lip survive at high rates; fish hooked deeply, in the gullet or gills, survive at very much lower ones, and the difference is large enough that it dwarfs most other handling variables.
That makes hook choice a welfare decision rather than a tackle preference. Pattern, size and how quickly a bite is answered all bear on where the hook ends up. A hook that is too small for the bait is frequently swallowed with it; a bait left until the fish has moved off with it is more often taken deeply than one struck early.
Where a fish is hooked deeply anyway, cutting the line close to the hook and leaving it is generally better for the fish than extracting it, and that is the opposite of most people's instinct.
Scientific evidence
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
- Understanding the Complexity of Catch-and-Release in Recreational Fishing — Reviews in Fisheries Science 15:75–167, 2007 (Scientific literature)Relied on for: Review of catch-and-release outcomes including hooking location, handling and the factors that bear on post-release survival.States this directlyCitation checked — the work exists and is described correctly
- Do we need species-specific guidelines for catch-and-release recreational angling? — Biodiversity and Conservation 14:1195–1209, 2005 (Scientific literature)Relied on for: Synthesis of terminal tackle effects on hooking injury and post-release survival across recreational fisheries.States this directlyCitation checked — the work exists and is described correctly
What the wrong hook looks like from the bank
Hook size is confusing enough that beginners frequently pick by guess and then attribute the consequences to the fish, the bait or the weather. The four symptoms are distinctive.
TOO SMALL FOR THE BAIT. The bait masks the point, so bites are felt and nothing connects. The hook has to sit where the point is clear when the bait is in a fish's mouth, which is why a large bait on a small hook is the classic missed-bite generator.
TOO LARGE FOR THE FISH. The fish cannot get it in, so the bait is picked at, taken and dropped, or stripped without the float or tip ever properly registering. Small hooks catch large fish reliably; large hooks do not catch small ones at all.
TOO FINE FOR THE FIGHT. A fine-wire hook opens under sustained pressure, and the symptom is unmistakable — the hook comes back straightened. It is a fish lost with the hook still in the angler's possession, which is the least harmful failure on this list.
TOO BLUNT, WHICH IS THE MOST COMMON AND THE LEAST SUSPECTED. A hook dragged over gravel or rock, or one that has been in a fish, will not penetrate. The test is to draw the point across a thumbnail: if it slides rather than catching, it is blunt. Beginners replace line, change bait and move swims to solve a problem a new hook solves in ten seconds.
AND THE BARB IS A WELFARE DECISION RATHER THAN A PERFORMANCE ONE. A barbless or crushed-barb hook comes out of a fish, and out of a person, far more easily. It is the strongest practical argument on this page and it costs almost nothing to act on. Many fisheries require it, which is a rule to check rather than assume.
Authoritative guidance
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- Angling Trust guidance for anglers — Angling Trust (Angling or fisheries organisation)Relied on for: Guidance to anglers on handling, unhooking and returning fish, and on the equipment choices that make those easier or harder.States this directlyCitation checked — the work exists and is described correctly
- Humane Harvesting of Fish: percussive stunning and percussive equipment — Humane Slaughter Association (Angling or fisheries organisation)Relied on for: Humane handling and dispatch of caught fish, and the welfare consequences of the decisions an angler makes at the bank.States this directlyNot yet checked
- Angling Times — Bauer Media (Specialist angling publication)Relied on for: Contemporary UK angling practice as reported by practitioners, including the setup errors beginners commonly make and the symptoms they produce.FishingHQ's interpretation of what it saysCitation checked — the work exists and is described correctly
- General angling website restatements of established technique — Various (Credible secondary source)Relied on for: Widely restated descriptions of common tackle faults and their symptoms, recorded as practitioner consensus rather than as scholarship.Background and mechanism onlyCitation checked — the work exists and is described correctly
Where to go next
Gear this affects
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Hooks
A mechanism edge from a record to the explanation beneath it. How tackle behaves is established practitioner knowledge reported consistently across independent traditions, and the label says that rather than claiming a test that was never run.
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice including rods, reels, lines, terminal tackle and the reasoning behind the choices.States this directlyCitation checked — the work exists and is described correctly
- Still-Water Angling — MacGibbon & Kee, 1953 (Specialist angling publication)Relied on for: Stillwater angling practice including rod design reasoning, line choice, hooks and the mechanics of playing fish.States this directlyCitation checked — the work exists and is described correctly
Related reading
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Hook sizing
A mechanism edge from a record to the explanation beneath it. How tackle behaves is established practitioner knowledge reported consistently across independent traditions, and the label says that rather than claiming a test that was never run.
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice including rods, reels, lines, terminal tackle and the reasoning behind the choices.States this directlyCitation checked — the work exists and is described correctly
- Still-Water Angling — MacGibbon & Kee, 1953 (Specialist angling publication)Relied on for: Stillwater angling practice including rod design reasoning, line choice, hooks and the mechanics of playing fish.States this directlyCitation checked — the work exists and is described correctly
How this compares
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
The kinds of hook, and what each is shaped for
Two records a reader is likely to be holding in mind at once, joined so that neither has to repeat the other.
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice including rods, reels, lines, terminal tackle and the reasoning behind the choices.States this directlyCitation checked — the work exists and is described correctly
- Still-Water Angling — MacGibbon & Kee, 1953 (Specialist angling publication)Relied on for: Stillwater angling practice including rod design reasoning, line choice, hooks and the mechanics of playing fish.States this directlyCitation checked — the work exists and is described correctly
Safety reading
What these connections rest on (1)
Scientific evidence — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Handling fish safely
The link between hooking location and post-release survival is established in the catch-and-release literature and is cited directly rather than restated as convention.
- Understanding the Complexity of Catch-and-Release in Recreational Fishing — Reviews in Fisheries Science 15:75–167, 2007 (Scientific literature)Relied on for: Review of catch-and-release outcomes including hooking location, handling and the factors bearing on post-release survival.States this directlyCitation checked — the work exists and is described correctly
- Do we need species-specific guidelines for catch-and-release recreational angling? — Biodiversity and Conservation 14:1195–1209, 2005 (Scientific literature)Relied on for: Synthesis of terminal tackle effects on hooking injury and post-release survival across recreational fisheries.States this directlyCitation checked — the work exists and is described correctly
History and culture
What these connections rest on (1)
Practitioner consensus — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
The history of the fish hook
A beginner explainer joined to the tradition that answers the question it leaves hanging. Written only where the record's own subject carries a specific historical fact it omits — in several cases the fact that explains why the thing is arranged so oddly — and refused for the general orientation pages where the only claim would be that fishing is old.
- The Compleat Angler, or the Contemplative Man's Recreation — Richard Marriot, 1653 (Reference work)Relied on for: Seventeenth-century English angling practice including tackle, hooks, lines and the fishing they were used for.States this directlyPassage read and verified
- Fishers' Craft and Lettered Art: Tracts on Fishing from the End of the Middle Ages — University of Toronto Press, 1997 (Scientific literature)Relied on for: Medieval and early modern angling tracts and the development of tackle, technique and the literature describing them.Background and mechanism onlyCitation checked — the work exists and is described correctly
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice across disciplines, including tackle, water reading and the conduct of a session.States this directlyCitation checked — the work exists and is described correctly
- Coarse Fishing — A. & C. Black, 1912 (Specialist angling publication)Relied on for: Classical coarse angling practice including approach to the water, presentation and the ordinary faults of a day's fishing.States this directlyCitation checked — the work exists and is described correctly
Sources for this page
- Freshwater Fishing — Macdonald & Jane's, 1975 (Specialist angling publication)Relied on for: Comprehensive angling practice including rods, reels, lines, terminal tackle and the reasoning behind the choices.States this directlyCitation checked — the work exists and is described correctly
- Still-Water Angling — MacGibbon & Kee, 1953 (Specialist angling publication)Relied on for: Stillwater angling practice including rod design reasoning, line choice, hooks and the mechanics of playing fish.States this directlyCitation checked — the work exists and is described correctly
- Understanding the Complexity of Catch-and-Release in Recreational Fishing — Reviews in Fisheries Science 15:75–167, 2007 (Scientific literature)Relied on for: Review of catch-and-release outcomes including hooking location, handling and the factors that bear on post-release survival.States this directlyCitation checked — the work exists and is described correctly
How FishingHQ labels evidence is explained in the evidence policy.