A fishing hook size chart looks simple until you notice that it counts in two directions. From the tiniest fly hooks up to a bass hook the numbers fall as the hooks grow, #32 to #1; then the scale flips to “aughts”, written 1/0, 2/0 and so on, and the numbers rise as the hooks grow, up to the 20/0 of a shark rig. Every beginner asks whether a #2 or a #4 is bigger, and the answer, the #2, is the one that feels wrong. Once the scale makes sense, the two charts below answer the practical question: which size for which fish, and which bait.
A #2 hook is bigger than a #4, and a 2/0 is bigger than a 1/0. The scale runs down to 1, then flips and runs up again, and nobody who learned it the hard way forgets.
What you need
- The hooks hub for the hook types, the parts of a hook and the circle-hook rules; this page is about size only.
- A ruler. The gap of the hook, point to shank, is the number to check against the chart, because that is what the size describes.
How the scale works
| Size | Gap, approximately | What it is for |
|---|---|---|
| #32 to #20 | Under 1/8 in (3 mm) | Midge and dry flies |
| #18 to #12 | 1/8–3/16 in (3–5 mm) | Trout flies, tiny bait hooks |
| #10 to #6 | 3/16–5/16 in (5–8 mm) | Bluegill, crappie, perch, trout on bait |
| #4 to #2 | 5/16–7/16 in (8–11 mm) | Walleye, small catfish baits, bass finesse |
| #1 and 1/0 | 7/16–1/2 in (11–13 mm) | Drop-shot and wacky hooks, walleye, small live bait |
| 2/0 to 3/0 | 1/2–5/8 in (13–16 mm) | Smallmouth, 4–5 in worms, channel catfish |
| 4/0 to 5/0 | 5/8–3/4 in (16–19 mm) | Largemouth on worms and creature baits, flukes, frogs |
| 6/0 to 8/0 | 3/4–1 in (19–25 mm) | Blue catfish on cut bait, big swimbaits, inshore |
| 9/0 to 12/0 | 1–1½ in (25–38 mm) | Flathead live bait, grouper, tuna |
| 13/0 to 20/0 | 1½ in (38 mm) and up | Halibut, sharks, big-game bait |
Read the number as gap, not length. The size tells you how far the point sits from the shank, which sets how much bait the hook can hold and how big a mouth it can hook; a long-shank Aberdeen and a short-shank octopus of the same size have the same gap and very different lengths. And the sizes are not a standard: each maker sets its own, so a Gamakatsu 2/0 and a Mustad 2/0 differ by a fraction, and a 3/0 extra-wide-gap worm hook has a bigger gap than a 3/0 octopus. The gap ranges above are approximate for that reason; the chart on the packet is the one to trust for a given brand.
Hook size by species and bait
The retail and guide consensus, refined by the species pages where they exist.
| Species | Hook type | Size | Bait |
|---|---|---|---|
| Bluegill, sunfish | Aberdeen or bait hook | #8–#12 | Worm piece, cricket |
| Crappie, perch | Aberdeen | #6–#10 | Minnow, small jig |
| Trout, stream | Single bait hook | #10–#14 | Worm, salmon egg |
| Bullhead | Bait hook | #4 to 1/0 | Nightcrawler |
| Walleye | Octopus or J | #4 to 1/0 | Minnow, leech, crawler |
| Smallmouth bass | Worm hook, drop-shot hook | 2/0–3/0; #1–1/0 drop shot | 4 in worms, tubes |
| Largemouth bass | Extra-wide-gap worm hook | 3/0–5/0 | 6–10 in worms, creature baits, flukes |
| Channel catfish | Circle | 2/0–4/0 (6/0 covers everything to mid-teens) | Cut bait, prepared bait on a treble #4–#6 |
| Blue catfish | Circle | 5/0–8/0 for chunks, 8/0–10/0 for heads | Cut shad, skipjack |
| Flathead catfish | Circle | 7/0–10/0, up to 12/0 for big live bait | Live bluegill, bullheads |
| Pike, musky | Treble or single | 2/0–5/0 | Lures, dead bait |
| Redfish | Circle | 1/0–3/0 | Shrimp, cut mullet |
| Snapper | Circle | 2/0–5/0 | Cut bait |
| Grouper | Circle | 8/0–12/0 | Live or cut bait |
| Tarpon | Circle | 3/0–7/0 | Live bait |
| Tuna | Circle | 7/0–10/0 | Live bait, chunks |
| Halibut | Circle | 8/0–16/0 | Herring, octopus |
Two rules from the species pages. For soft plastics, match the hook to the bait’s length: a 4 in worm takes a 2/0–3/0, a 7 in worm or a creature bait a 4/0–5/0. For catfish and other bait fishing, match the hook to the bait’s size rather than the fish’s, and use a circle hook, which sets itself in the corner of the mouth when the fish runs; the hooks hub has the rules on where they are required.
Treble hooks
Trebles use the same numbers, and the same reversal, but the common sizes run #8 (smallest) through #6, #4, #2, #1, 1/0, 2/0 and 3/0. Crankbaits ship with #4 and #6; the reviewers’ rule is #4 on half-ounce lipless baits and squarebills, #2 on 4–5 in topwaters, and one size up on the front hook of a crankbait to improve hookups without changing the tail action. A heavier or lighter replacement treble changes the weight and can sink a suspending jerkbait or float a topwater differently; the crankbait hub explains why.
Choosing a size, step by step
- Start from the bait, not the fish. The hook has to hold the bait with the point clear: a nightcrawler on a #4, a 6 in worm on a 4/0, a bluegill through the back on an 8/0.
- Check the mouth. A bluegill cannot take a 1/0; a flathead swallows a 10/0 whole. The species table gives the range.
- Pick the type, which changes the gap at a given size: extra-wide-gap for plastics, circle for bait, Aberdeen for small mouths and snaggy timber.
- Go one size smaller in clear water and for finicky fish, one size larger in cover and for big baits.
- Read the packet. The maker’s chart, drawn to scale, is the only exact one; hold a hook against it if in doubt.
Mistakes to avoid
- Reading the scale the wrong way. A #6 is smaller than a #4; a 6/0 is bigger than a 4/0. The slash is the hinge.
- Choosing by the fish’s weight. A 20 lb catfish bites a 2/0 with a small bait on it; a 2 lb bass takes a 5/0 with a big worm. Bait first.
- A 4/0 on a 4 in finesse worm. Too much steel kills the action; drop to 2/0 or a #1 drop-shot hook.
- Assuming brands match. Check the gap when you change makers.
- Burying a big hook in a small plastic. The point must clear the bait on the set; if it cannot, the hook is too big or the plastic too small.
When to use something else
Size is one of three hook decisions. The type is the second, and the hooks hub covers the ten styles; the circle-hook page under it covers the third, whether the law requires a circle hook for the fish you are after. For the rigs that put these hooks to work, see jigs and rigs and the catfish hub.