If you’ve spent any time at the fly tying bench – or sorting through packets of hooks – you’ve probably come across a familiar frustration: hook sizes often don’t match up. One brand’s size 12 can look more like another brand’s 14, and comparing barbed to barbless hooks can make things even more confusing. So why does this happen?
Let’s explore why hook sizing may feel inconsistent – and how you can make better sense of it.
No Global Standard
To begin with, there’s no universal or enforced system for fly hook sizing. The numbers are more of a convention than a precise measurement. In general, higher numbers tend to mean smaller hooks (e.g., size 20 is very small; size 6 is much larger), and once you go past size 1, the system often flips into the “aught” range (1/0, 2/0, etc.).
However, beyond that rough framework, manufacturers are largely free to define sizes in their own way – often based on the type of fishing or flies the hook is designed for. This may explain why the same size from two different brands can look and behave quite differently.
Above: All these hooks are size 12
Gape, Shank, Wire: What May Really Matter
While size numbers are convenient, it’s often the proportions of a hook that make the biggest difference in how your fly ties and fishes.
- Gape (the distance between the hook shank and the point) can vary widely. Barbless hooks, in particular, often have wider gapes to help with hook-hold and penetration, which can make them look noticeably larger – even if they’re marked with the same number as a barbed hook.
- Shank length may also play a significant role. A hook with a longer shank (like a 2x long) will give your fly a stretched profile – handy for things like damsels or extended dries. On the other hand, a 1x short hook in the same size can produce a compact, punchy pattern for flies like buzzers or caddis pupa.
- Wire thickness may change as well. Some hooks are designed to be fine and light for dry flies, while others are made heavier for durability, depth, or species with hard mouths. These subtle variations may shift your fly’s performance more than the number on the packet suggests.
Barbless Hooks Often Appear Bigger
Barbless hooks have become increasingly popular – especially for anglers practicing catch-and-release or fishing on barbless-only waters. However, they often appear larger at a glance.
This may be due to:
- A wider gape
- More open or beaked point profiles
- Shank shapes that differ slightly from traditional barbed designs
While this may offer better hooking mechanics and improved fish retention, it can make it trickier to match hook sizes across brands or between barbed and barbless options.
Best Practice: Compare Within the Same Hook Family
If there’s one reliable approach, it’s this: stick to the same hook family when comparing sizes.
For example, if you like the Hanak 390bl in size 16 for your Klinkhammers, you’ll likely find the size 14 or 18 in the same model behaves as expected. But trying to match that size to a Fulling Mill, Partridge, or Tiemco equivalent may not give you the same results.
When switching brands or models, it may be worth tying a sample fly or laying hooks side-by-side before committing to larger purchases. Where available, photo comparisons or sizing charts can also help – but they may not always tell the full story.
Final Thoughts
The lack of standardisation in fly hook sizes can feel inconvenient – but it also gives fly tyers the freedom to choose what works best for each pattern and situation. Once you start focusing on function – gape, shank, wire, and overall shape – you may find it easier to get consistent results at the vice and on the water.
And if you’re not sure, ask your local fly shop or guide. We’ve spent plenty of time lining up hooks and scratching our heads too.
Tight lines, and may your hooks always hold firm (regardless of what number’s printed on the packet).
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