How to Fly Fish | Fly Fishing Tippet – Making Sense of Its Numbering System

3x, 4x, 5x… it gets confusing. Here’s how to simplify and make sense of those designated numbers.

No trout fishing setup is complete without a tippet holder. | Photo by Jasper Taback

If you wonder why trout anglers get a bad rap. Well, why do we need our own tippet sizing system that makes no sense to other fly anglers? If you’re fishing for saltwater species – or most freshwater species, for that matter – tippet sizes will be written in pound-test. However, in the trout fishing world, the “x”-system nonsense is standard. It’s antiquated, it’s silly, but it’s worth understanding. Here’s all you need to know. 

Diameter, Not Pound-Test

Rather than describing the tippet’s strength – or pound-test – the “x” is shorthand for the tippet’s diameter. You’ll see tippet starting at 0x, going all the way up to 8x. 0x tippet is 0.011” in diameter, and every step up in number is a thousandth of an inch thinner. 1x is 0.010”, 2x is 0.09”, and so on – up to 8x, which is 0.003” in diameter. If you want the approximate pound-test for each, here’s a helpful chart.  

Why Tippet Size Matters

Using the correct tippet size allows your fly to cast properly and move naturally with the current. If your tippet is too heavy for your fly, it will pull the fly unnaturally through the current. If your tippet is too light for your fly, you won’t have the stiffness needed to turn the fly over during your cast and let it land properly on the water.

How to Match Your Tippet to Your Fly

It can be pretty simple. Many trout anglers abide by the rule of 3 – divide the size of the fly by 3, and you’ll get an approximate tippet size. For example, a size 15 fly is a good match for 5x tippet. 

A word of caution: Many anglers use tippet that is too light. The lighter the tippet, the longer it takes to play and land a fish – in an effort to keep trout happy and healthy, I like to err on the heavier side when I select my tippet. Try to use 4x tippet with a size 15 fly – I know it breaks the rule of 3, but it typically works just fine. If you’re finding that your drift is unnatural or trout are refusing your fly, go ahead and bump up to 5x. 

Give It a Try

As with most fly fishing lessons, it’s best to learn by doing. Pick up a few spools of tippet, and see what it feels like to fish a size 15 fly on 4x compared to 5x. Pretty soon, you’ll get a feel for the relationship between fly size and tippet diameter, and it will become second nature. It seems complicated – but, at the end of the day, it’s just fishing.