To anyone who isn’t familiar with fly-fishing, the how-to articles, blog posts or fly shop advice must sound like some weird SAT math question. They’re full of numbers – numbers that don’t necessarily correlate with anything in real life.

“For that stream, I’d recommend a 9-foot 5-weight rod and a size 14 fly on a 12-foot leader with a 5X tippet.”

Huh?

In hopes of simplifying things for the newbie, About.com presents a guide to fly-fishing by the numbers – a quick reference to the numerical nomenclature and how it translates to actual fishing.


(We’ll show our work.)

The example above uses numbers that describe five things:

--The length of the rod (“9-foot”)

--The weight of the rod and the line that matches it (“5-weight”)

--The size of the fly (“size 14”)

--The thickness (or fineness) of the leader to which the fly is tied (“5X tippet”)

--The length of the leader (“12-foot”)

Let’s break it down.

Rod Length

Most fly-fishing is done with rods between seven and nine feet long. The shortest ones are for small mountain streams; the nine-footers can be for anything from a trout stream to an ocean jetty, depending on the rod/line weight (more on that below.) For all but the tiniest brooks, a rod eight to nine feet long in the right weight is a good all-around trout fishing rod. Which brings us to…

Rod/Line Weight

This does not refer to how many ounces the rod weighs. It does refer to the weight of the line. A 5-weight line is considered an all-around trout fishing line. A 3-weight line might be helpful on a small, shallow trout stream, while a 9-weight line is what you’d use to cast large flies a relatively long distance for big saltwater fish like striped bass.

The smaller the number, the lighter and more delicate the line.

Each fly rod is designed, by its thickness and taper, to throw a particular size of line well. So when we say a 5-weight rod, what we really mean is a rod designed to cast a 5-weight line. Got it?

Fly Size

The smaller the number, the bigger the fly. I know. Don’t ask.

The number actually refers to the size of the fly’s hook, which governs the proportions of the whole fly. In general, the size 14 referred to in the example translates into a fly about a half-inch long, a very common size for the aquatic insects trout eat. A size 20 fly is a tiny thing; three of them would fit on a dime. Size 2 hooks are bigger and used to make flies that imitate minnows; the can be three inches long. And there are much bigger ones, tied on much bigger hooks.

Leader Length

Remember, a fly line isn’t a length of what most people think of as fishing line – thin, clear monofilament. A fly line is more like a vinyl cord. It’s tapered so that it’s thicker and heavier at the front end, to make it easier to cast. But you do need a short length of clear fishing line at the end, to which you tie the fly. That length of clear line is called the leader, and it too is tapered. Which brings us to…

Tippet Size

Once again, smaller number, bigger object. In this case the object is the thin part of the leader, where the fly is tied on. It’s called the tippet. The number does not refer to breaking strength (though by coincidence, a 5X tippet is about five-pound test.) Rather, it’s an arcane measure dating back to the days before nylon, when leaders were made of silkworm gut. You select your “X” tippet size based on the size of the fly you’re using, and there’s a formula: divide the hook size by 3. For a size 12 fly, use 4X tippet. For a size 20, use 6X.

You could describe tippets by their actual diameters (5X is .006 inch, 2X is .009 inch, 7X is .004 inch), but almost no one ever does.

Breaking strength does come into play, of course. If you hook a good-sized trout on a thin tippet like 7X – and it happens all the time – you’d better play the fish carefully, lest you break it off.

Putting it All Together

If you’re looking to fly-fish for trout, here’s what you need: an 8- to 9-foot rod for a 4- or 5-weight line; a 9-foot leader with a 5X tippet; spools of 4X, 5X and 6X tippet material, to replace what you snip off changing flies or to make your tippet thicker or finer, as conditions require; and a basic assortment of flies, sizes 12 through 18.

See? It’s simple as that. And don’t worry if you don’t retain it all. Unlike the SAT, you’re free to use your smartphone to check out Flyfishing.About.com.