How Do Fly Fishing Hook Sizes Work?

Fly fishing is a popular sport and hobby, and understanding the size of your hooks is essential to success. The size of your hook will determine how big of a fish you can catch, what type of bait and presentation you should use, and how deep your line should be in the water.

To understand how fly fishing hook sizes work, it’s important to know that there are two types of measurements used: the imperial system and the metric system.

The imperial system is measured in inches or fractions of an inch, and uses numbers from 12 (smallest) to 2/0 (largest). The higher the number, the larger the hook.

In most parts of the world, this system is used for fly fishing hooks because it’s easier to remember than the metric system.

The metric system measures in millimeters and uses numbers from 0 (smallest) to 12/0 (largest). This system is more precise than the imperial system and may be used when Targeting very small fish or when using very specific bait presentations.

Size Matters

The size of your hook will determine what type of bait you should use. For example, if you’re using an 8/0 hook, you’ll want to use larger bait such as night crawlers or shrimp since these will fit on a bigger hook. Conversely, if you’re using a size 14/0 hook, you’ll want to use smaller baits such as grubs or worms since these will fit on a smaller hook.

Depth Matters

The depth at which you should fish also depends on your hook size. For example, if you’re fishing with an 8/0 hook, then you’ll want to have your line deeper in the water than if you were using a 14/0 hook. This is because larger hooks can catch bigger fish that tend to stay deeper in the water.

Presentation Matters

Lastly, presentation matters when it comes to fly fishing hooks sizes. The size of your fly will determine which type of presentation technique works best for catching fish. For example, if you’re using an 8/0 hook then a wet-fly technique works best since this requires more weight due to its larger profile.


Understanding how fly fishing hook sizes work can help ensure that anglers have success out on the water by making sure they have chosen the right size for their Target species and conditions. Knowing which measurements are used for hooks as well as understanding how depth and presentation play into choosing a suitable size can make all difference between catching something or going home empty-handed.

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Lindsay Collins