Fishing hook sizes can be a source of confusion for many anglers.
We will explain fishing hook sizes – and the two numbering systems used to classify them – below.
And we’ve also included some information on good hook sizes for various different species of fish.
Freshwater hooks and small saltwater hooks (size 32 to 1)
It is counterintuitive, but with this category of hooks (those without a backslash and a zero after the number) the bigger the number, the smaller the hook.
The numbers in fishing hook sizes start out at 32, which are very small hooks and are scarcely used, and run up to a size 1 as the largest. Often these numbers have a hash in front of them to denote that it is a size they are referring to.
Hooks are sized based on the gape – the distance between the hook point and the shank.
So while as a general rule a #4 hook might be an inch or so long, that’s always the case as you have long shanked hooks that are elongated, and circle hooks which are shorter (for a full rundown of all the different hook types – including worm hooks, Siwash hooks, circle hooks, jig hooks, octopus hooks and baitholder hooks – check out our article on this).
There is a labeling system to account for these differences and help anglers understand them. Fly fishers and fly tyers are very familiar with this system (click here to read our article on choosing hooks for fly tying or here to access our tool for this purpose).
1X long – the hook is as long as the standard length in the size above, so a 1X long in #4, would be as long as a size #3 hook. A 2X long hook in a size #4 would be as long as a standard hook in #2 and so on.
The same principle applies with other characteristics so you can have 1X fine, 1x heavy, 1x short and so on.
The graphic below gives you some idea of the dimensions in inches and millimetres of standard hooks in the various sizes.
Fishing hook size chart
Larger fishing hooks (size 1/0 and up)
Once you go bigger than size 1, fishing hooks have an “aught” designation – this just means the numbers have /0 after them. This system works in reverse – the larger the number the larger the hook. So the smallest in the aught designation is a 1/0 – slighty over an inch long in the standard shape. Then you go right up to a 20/0 big game hook.
Most often the aught hooks are used in saltwater fishing for targeting larger fish, although they can be used for big freshwater fish such as catfish.
Treble hooks and sizing
Treble hooks follow the same sizing as standard hooks.
Most often trebles are used with lures and are relatively small in size – say #12 or #14 – particularly where there are multiple sets of the trebles on the lure like you see in many crankbaits.
Hook sizes for different fish species
Choosing the right hook type and size reduces the damage to the fish especially where you can avoid the fish swallowing the bait.
Consider using barbless hooks if you are fishing catch and release. These are much easier to remove from the fish’s mouth than barbed hooks and treble hooks.
Hook sizes for trout
Hook sizes for trout tend to run from about size 14 through to size 8 as a general rule, although there are a number of factors at play in choosing what’s the right size (learn more here).
Hook sizes for bass
Bass have an oversized mouth and can pull line in short bursts, so the best hooks are relatively large and strong. We suggest 1/0 through to 3/0 hooks are perfect for fishing for largemouth bass. Read more in our article on hook sizes for bass.
Hook sizes for catfish
Catfish are strong fish with a soft mouth that is relatively easy for the hook point to penetrate. Hooks in the 3/0 up to 5/0 size range have enough strength to not bend when you are fighting a big catfish (learn more here on catfish hook sizes)
Hook sizes for crappie
The best crappie hooks are a bit bigger than you might think given the comparatively small size of the fish. They do have a relatively large mouth and you want to avoid them swallowing the bait, so anything from size 6 through to 2 is acceptable (learn more here on crappie hooks).