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    Relying solely on hook numbers is dangerous. Here’s why:

    These are "aught" sizes. As the number before the slash gets larger, the hook gets larger. A 10/0 is a massive hook for ocean predators. Fishing Hook Size Chart (Approximate MM)

    Before looking at the numbers, it’s important to know what you are actually measuring. When we talk about hook size in mm, we are usually referring to the —the distance between the hook point and the shank.

    | Standard Size | Approx. Gap (mm) | Typical Target Species | Best Bait Size | | :--- | :--- | :--- | :--- | | | 1.5 mm | Tiny Minnows/Micro Fish | Micro Midge larvae | | Size 28 | 2.0 mm | Small Trout | #28 - #24 Flies | | Size 24 | 2.5 mm | Trout, Bluegill | Small maggots | | Size 20 | 3.0 mm | Trout, Roach | Single maggot | | Size 18 | 3.5 mm | Trout, Skimmers | Small worms | | Size 16 | 4.0 mm | Grayling, Large Trout | Large maggots | | Size 14 | 4.5 mm | Bass, Walleye | Small lures/Spinners | | Size 12 | 5.0 mm | Bass, Bream | Medium worms | | Size 10 | 5.5 mm | Carp, Tench | Sweetcorn/Pellet | | Size 8 | 6.0 mm | Large Bream, Catfish | Double corn | | Size 6 | 7.0 mm | Bass, Sea Trout | Medium crabs | | Size 4 | 8.0 mm | Pike, Small Bass | Large worms | | Size 2 | 9.0 mm | Bass, Flounder | Minnows | | Size 1 | 10.0 mm | Bass, Sea Fish | Small fish strips |

    Before diving into the charts, it is important to understand why the metric system is superior for hook selection.

    Circle hooks and jig heads are increasingly popular among carp, catfish, and bass anglers. Because these hooks are often measured by their wire diameter or the specific width of the hook bend, millimeters have become the industry standard for high-precision terminal tackle.

    Note: Measurements are approximations of the (the distance between the hook point and the shank), as shank lengths vary by style (Aberdeen, O'Shaughnessy, etc.).

    | Size | Gap (mm) | Size | Gap (mm) | |------|----------|------|----------| | #32 | 1.5 mm | 1/0 | 11 mm | | #24 | 2.0 mm | 2/0 | 12.5 mm | | #20 | 2.5 mm | 3/0 | 14 mm | | #16 | 3.5 mm | 4/0 | 16 mm | | #14 | 4.0 mm | 5/0 | 18 mm | | #12 | 4.5 mm | 6/0 | 20 mm | | #10 | 5.0 mm | 7/0 | 22 mm | | #8 | 6.0 mm | 8/0 | 24 mm | | #6 | 7.0 mm | 9/0 | 26 mm | | #4 | 8.0 mm | 10/0 | 28 mm | | #2 | 9.0 mm | 12/0 | 32 mm | | #1 | 10.0 mm | 14/0 | 36 mm |