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Is a size 4 hook bigger than a size 8? Yes: the higher the number, the smaller the hook. Then you hit 1 and the series flips: a 1/0, said “one-aught,” is bigger than a 1, a 2/0 is bigger than a 1/0, and so on [1]. Here is how to read that scale, what it means in inches for one maker, and the sizes public agencies suggest for each fish and bait.
Why the number rises as the hook shrinks
The series counts down to 1 and then changes notation: on one maker’s product page, sizes 1, 1/0, 2/0 and 3/0 grow one after the other [1]. State agency guides work the same way: sizes 10, 8 and 6 suit small-mouthed fish such as panfish and stream trout, while 2, 1 and 1/0 are for bigger fish such as walleye, northern pike, muskellunge and largemouth bass [2].
The table gives the real dimensions of one specific model, the Mustad 39940NP offset circle hook. From the 1 to the 10/0, the gap goes from 0.35 to 0.91 in. and the length from 0.69 to 1.83 in., about 2.6 times more; the wire goes from 0.042 to 0.104 in [1]. The steps are not even: about 0.03 in. of gap between the 1 and the 1/0, but about 0.08 in. between the 8/0 and the 9/0.
| Size | Gap (in.) | Length (in.) | Wire (in.) |
|---|---|---|---|
| 1 | 0.35 | 0.69 | 0.042 |
| 1/0 | 0.38 | 0.76 | 0.045 |
| 2/0 | 0.42 | 0.83 | 0.049 |
| 3/0 | 0.46 | 0.91 | 0.052 |
| 4/0 | 0.50 | 1.00 | 0.056 |
| 6/0 | 0.60 | 1.20 | 0.072 |
| 8/0 | 0.73 | 1.46 | 0.086 |
| 10/0 | 0.91 | 1.83 | 0.104 |
Maker’s dimensions for this model only (gap converted from millimeters): another model or another brand gives other values.
Three dimensions matter. The The distance between the point of the hook and the shank, also called the gape. tells you what the fish’s mouth can take; the length runs from the eye to the bottom of the bend; and the wire diameter tells you how strong the hook is [3]. The drawing below names each part, on a J hook and on a circle hook.
The same number, two different hooks
No standard fixes these sizes. The Atlantic States Marine Fisheries Commission says so plainly: the measuring convention varies widely between manufacturers, and even between hooks from one manufacturer, so that a 5/0 from one company may be the same size as an 8/0 from another [4]. A fishing site gives a milder example: a 3/0 Gamakatsu weighted hook has a wider gap than a 3/0 Owner weighted hook [3].
Shank length matters as much as the number. Minnesota recommends a long shank for bulky baits such as nightcrawlers [2], and New York notes that a long-shank pattern, an Aberdeen style for example, can help when you need to remove a swallowed hook [5].
Which number for which fish?
These are the sizes public agencies print in their beginner guides, from Minnesota to Pennsylvania. They agree on the pattern: small hooks (6 to 12) for bluegill, perch and stream trout, hooks of one to a few aughts for big predators [2, 5, 6, 7, 8, 9]. Treat them as a starting point and check your state’s guide for local favorites.
| Fish (name used in the guide) | Suggested size | Bait or detail |
|---|---|---|
| Sunfish (bluegill) | 10 (Minnesota); 8 or 10 (New York); 6 to 12 (Pennsylvania) | Piece of nightcrawler, wax worm or meal worm under a bobber |
| Yellow perch | 8 (Minnesota); 6 (New York) | Small minnows, worms, wax worms |
| Crappie | 6 (Minnesota and New York) | Small minnows or wax worms |
| Stream trout | 6 (Minnesota); 6 to 10 depending on bait size (New York) | Worms, fish eggs, maggots |
| Trout | Single hook, 10 to 16 (Missouri) | Salmon eggs |
| Trout | Treble, 16 to 18 (Missouri) | Cheese or dough bait |
| Bullhead | 2 (Minnesota); 4 or 6 (New York) | Dough balls, nightcrawlers, chicken liver, fished on the bottom |
| Walleye | 2 (Minnesota) | Nightcrawlers, leeches, 2- to 4-inch minnows |
| Smallmouth bass | 1 (Minnesota) | Crayfish, 2- to 4-inch minnows, nightcrawlers |
| Largemouth bass | 1/0 (Minnesota) | Frogs, 3- to 6-inch minnows, crayfish |
| Catfish | 1/0 (Minnesota); 2 to 1/0, a stout hook (New York) | Frogs, nightcrawlers, crayfish, minnows |
| Northern pike | 1/0 or larger (Minnesota) | 4- to 8-inch minnows |
| Big-river catfish | 6/0 to 8/0 circle hooks on a rod; 8/0 or 12/0 circle hooks when drifting (Missouri) | Two hooks 18 inches apart for drifting |
Guides from 2010 (Minnesota) to today: a rough guide, not an instruction for your waters.
The right number depends on the bait as much as on the fish. For trout, Missouri gives a single hook of 10 to 16 for salmon eggs and a treble of 16 to 18 for cheese or dough baits [10], while New York suggests 6 to 10 for worms and other natural baits, depending on the bait’s size [7]. Minnesota sums up the rule: a hook big enough to hold the bait, small enough to fit in the fish’s mouth [2].
The circle hook, which sets itself
A circle hook has its point turned back toward the shank: the ASMFC defines it as a non-offset hook with the point turned perpendicularly back to the shank [4]. It sets in the corner of the mouth as the fish moves off, so you do not set the hook; Missouri makes that point for big-river catfish [9]. In striped bass trials summarized by the ASMFC, deep hooking was nearly three times less frequent with non-offset circle hooks than with J hooks (5.6% versus 15.0%) [4].
| Measure | J hook | Non-offset circle hook |
|---|---|---|
| Deep hooking (2001 trial) | 15.0% | 5.6% |
| Fish landed per detected strike (2002 trial) | 42% | 27% |
Two different trials, from the ASMFC Special Report No. 77 (2003).
The same report flags a downside: in another trial, anglers using J hooks landed a fish on 42% of detected strikes, versus 27% with non-offset circle hooks [4]. More fish released unharmed, a few fewer in the net: it is a choice, not a given.
Barbless hooks: what the rules say
Rules differ by state, park and water. Yellowstone National Park, for example, requires hooks with barbless points or barbs pinched down with pliers, and allows lures only one hook, with single, double or treble points [11]. The park’s own reasoning: barbless hooks reduce injuries and handling time and improve the overall condition of trout in heavily fished waters, and a single-pointed hook is its recommended choice [11].
Before you go: three checks
- The rules of the water: state regulations, park rules, barbless requirements, hook type and number.
- The hook’s dimensions: gap and length from the maker’s page, not only the number.
- The fish’s mouth and the bait: big enough to hold the bait, small enough to fit in the mouth.
A rule is read with its date: the sizes here come from guides published from 2010 to today, and the Yellowstone rules from its 2026 booklet. Before the next trip, reopen the text that applies to your water.
Gear related to this article
No affiliation: no commission, no sponsored products.
Pro-Knot Fishing Knots (waterproof knot cards)
Twelve fishing knots, the improved clinch among them, illustrated on six waterproof plastic cards held by a brass grommet: pocket-size at 3½ by 2¼ inches, made for a tackle box.
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Worth watching
A fishing-media video on hook sizing, gauge, gap and length, and on why one number can mean different sizes between makers: the same point the ASMFC report makes. Published by a US tackle-and-tips company.
The video is hosted by YouTube (Google): nothing loads until you play it, and Google may then set cookies.
FAQ
Is a 1/0 hook bigger or smaller than a 1?
Bigger. The series counts down to 1 (the higher the number, the smaller the hook), then the 1/0, 2/0 and 3/0 sizes grow. On Mustad’s product page the gap goes from 0.35 in. for the 1 to 0.38 in. for the 1/0 and 0.42 in. for the 2/0. The 10/0 reaches 0.91 in.
What hook size should a beginner buy?
Minnesota and New York beginner guides suggest sizes 6 to 10 for small-mouthed fish such as sunfish and stream trout, with worms or eggs. Add a few larger hooks, around 1/0, if you plan to fish for bass or catfish, and check your state’s regulations for any limits on hook type.
Is a size 6 the same from every brand?
No. The ASMFC says the measuring convention varies widely between manufacturers, and even between models from one manufacturer: a 5/0 from one company may equal an 8/0 from another. Compare gap and length when the maker publishes them rather than trusting the number alone.
Do I need barbless hooks?
Only where the rules say so. Yellowstone requires barbless hooks or barbs pinched down with pliers, and many other waters have similar rules. Check your state’s regulations booklet and the posted rules of the water, and pinch the barb if in doubt.
Why choose a circle hook?
Its point turned toward the shank makes it set in the corner of the mouth. In striped bass trials summarized by the ASMFC, deep hooking was nearly three times less frequent than with a J hook (5.6% versus 15.0%), though anglers also landed fewer fish.
Sources
- Mustad, product page for the Demon Offset Circle Hook 1X Strong (39940NP), size and dimension table, accessed November 5, 2026. bedrift.mustad.no https://bedrift.mustad.no/uk/products/39940np ↩
- Minnesota Department of Natural Resources, MinnAqua programme, “Tackling Your Tackle Box”, leader’s guide, chapter 5, lesson 4, 2010, accessed November 5, 2026. files.dnr.state.mn.us https://files.dnr.state.mn.us/education_safety/education/minnaqua/leadersguide/chapter_5/5_4_tackling_your_tackle_box.pdf ↩
- Salt Strong, “The Truth About Hook Sizes (And What You Need To Know)”, accessed November 5, 2026. saltstrong.com https://www.saltstrong.com/?p=38583 ↩
- Atlantic States Marine Fisheries Commission, “Circle Hook Definition and Research Issues”, Special Report No. 77, July 2003, accessed November 5, 2026. mrc.virginia.gov https://mrc.virginia.gov/Notices/ASMFC_SR77_Circle-Hook-Definition.pdf ↩
- New York State Department of Environmental Conservation, “Fishing for Panfish”, accessed November 5, 2026. dec.ny.gov https://dec.ny.gov/things-to-do/freshwater-fishing/learn-to-fish/tips-skills/panfish ↩
- Pennsylvania Fish & Boat Commission, “All About Bluegill”, accessed November 5, 2026. pa.gov https://www.pa.gov/agencies/fishandboat/fishing/all-about-fish/catch-pa-fish/bluegill ↩
- New York State Department of Environmental Conservation, “Fishing for Stream Trout”, accessed November 5, 2026. dec.ny.gov https://dec.ny.gov/things-to-do/freshwater-fishing/learn-to-fish/tips-skills/stream-trout ↩
- New York State Department of Environmental Conservation, “Fishing for New York’s Big Cats”, accessed November 5, 2026. dec.ny.gov https://dec.ny.gov/things-to-do/freshwater-fishing/learn-to-fish/tips-skills/fishing-for-new-york-big-cats ↩
- Missouri Department of Conservation, “Big River Catfishing”, accessed November 5, 2026. mdc.mo.gov https://mdc.mo.gov/fishing/species/catfish/big-river-catfishing ↩
- Missouri Department of Conservation, “Trout: Fishing Tips”, accessed November 5, 2026. mdc.mo.gov https://mdc.mo.gov/fishing/species/trout/trout-fishing-tips ↩
- National Park Service, Yellowstone National Park, “2026 Fishing Regulations”, accessed November 5, 2026. nps.gov https://www.nps.gov/yell/planyourvisit/upload/2026-Fishing-Regulations-digital.pdf ↩
Fact-checking, regulations, and safety
Arnaud Couderc reviews our contributors’ articles and writes for Outfarer about regulations, safety, fishing, the ocean, and outdoor activities. He traces every rule back to its official text and every number to its source, so you head out with solid benchmarks.
