How to Pick The Right Fly Line

As a beginner, if you thought picking a fly rod was tough with all the options on the market, you’ll probably feel like that’s child’s play compared to picking out a fly line. From sink-tips to intermediate lines, Spey and Skagit kits, to quarter, half, and full-size heavy lines, it’s not easy to wade through all the noise here and pick the right line for your fly rod. Over the years, we’ve fished for various species around the world, all requiring different fly lines and rods. In an effort to simplify the line selection process, we will explain what you need to look for and give you some solid background knowledge so you can pick the right line for your fly fishing needs.

Fly Line Anatomy

Fly lines are made up of running line, a rear taper, belly, and front taper. The way that these components blend together dictates how a fly line will behave, and shows you what a fly line was designed to do.

Most fly lines are around 90 feet, although some are longer.

Your fly rod is designed to cast weighted line; the part of the fly line with the weight that loads your rod, so you can effectively cast, is the head. The head is made up of the front taper, belly, and rear taper, and can be anywhere from the first 30 feet of a fly line to the first 60 feet of the line.

Running line is thin and level. It doesn’t have a taper, or very much weight. It’s designed to give you more distance, and to give you more room between your fly line and backing on your reel.

Line Weight

Fly rods are designed to cast a certain weight of fly line. The larger the weight, the larger the fly that rod can easily throw. Each fly line has a standardized weight, set by the American Fly Fishing Trade Association (AFFTA).

A 5-weight rod is designed to cast a line that weighs 140 grains, although AFFTA considers a line weighing anywhere from 134 – 146 grains a 5-weight.

These line weight standards are largely suggestions these days, because a lot of fly rod companies are building rods that are stiffer. A term you’ll hear to describe this is “faster.” It means that less of the rod bends during the cast. So a rod designed to handle the regular duties of a 5-weight – dry flies, nymphs, and smaller streamers – might need a heavier line to properly load it. A heavier line adds more weight to the casting process, which will slow the rod’s action down, forcing it to bend more.

This has led to the rise of quarter, half, and full-size heavy lines. So the line might weigh 160 grains—the target weight for a 6-weight line—but it’s labeled as a 5-weight line, designed to be thrown on a 5-weight rod.

I know, that’s confusing. It’s largely a result of rod and line companies trying to complement the work the other is doing, and in the end, it makes it tough to know what fly line you’re really buying, especially if you’re new to the sport. That’s why understanding fly line design, tapers, and line weights is key to picking the right line for your rod.

Generally speaking, if you’re using your rod for all-around trout fishing, a line that’s true-to-weight (hits the AFFTA standard for line weight) up to a half-size heavy is generally your best bet. That line will handle throwing a wide range of dry flies, nymphs, and even some smaller streamers.

And now that we understand a fly line’s anatomy, let’s look at those other important aspects of picking a line.

Fly Line Taper

The most important consideration aside from the line’s actual weight (is it quarter, half, or full-size heavy) is its taper. Lines with short, aggressive heads are designed to cast large flies and deliver those casts quickly. Lines with longer, more gradual heads are great for more delicate presentations, like laying down dry flies on clear water.

For most trout fishing, I favor the Scientific Anglers Infinity line. It has a taper that strikes a great balance between enough weight to turn over streamers and heavier nymph rigs, but it’s still delicate enough for a lot of dry fly work.

It has about a 50-foot head, which is perfect, since most trout fishing requires casts in that 30-60 foot range. That means, for the majority of my casts, I’ll be casting and mending the head of the line, which is easier to move and manipulate than the running line.

Now, compare the taper of that Infinity line with this Titan Long taper, also from Scientific Anglers:

The head is shorter, and look at how aggressive that taper moves. The weight is packed in the first 15 or so feet to aid in casting heavy, large flies and to do so quickly.

Finally, look at the taper diagram for the Trout Expert line from Scientific Anglers:

The head on this line is nearly 70 feet long, and look at how gradually the taper moves from thick to thin. This is a line designed to gradually and softly lay out flies, so it’s going to be a great choice for anglers looking for a dry-fly specific line.

Picking Your Perfect Line

Alright – we know about fly line anatomy, and we’ve seen a few different tapers. Plus, we understand that some fly lines are heavier than others, even if they’re both labeled as 5-weight. So how do you use this information to pick the right line?

• For all-purpose trout fishing, it’s hard to beat the versatility of a half-weight heavy size line with a taper like the Scientific Anglers Infinity. You have enough weighted line to handle mending and casting to distance, but the line isn’t so heavy that it won’t softly lay down dry flies when the situation calls for it. From hopper-dropper rigs to nymph setups to larger single dries, this taper style is hard to beat.
• For dry flies, you’ll love a true-to-weight line with a long head and gradual taper. It won’t be the easiest to cast in the wind, but this line makes up for that by laying down flies so softly. A small dry-dropper rig works well on this line, too.
• For big bugs and bigger fish, get those more aggressively tapered lines. They’re specifically designed to handle these big flies and the demands of turning them over.

What About Sinking Lines?

So far, we’ve focused entirely on floating lines, and that ignores a huge portion of lines out there – sink-tips and full-sink lines.

These are built for fishing streamers, wet flies, and nymphs, often in stillwater environments, although you’ll see a lot of sink-tip lines used for fishing streamers in rivers.

The key to understanding these lines is reading the line’s sink rate, which is often expressed in how many inches it sinks per second (IPS). A 7IPS line sinks quicker than a 2IPS line. For deep water, or fishing streamers in fast-moving rivers, a faster sink and a longer sink-tip are ideal.

To fish wet flies or nymphs at a certain depth in stillwater, or slower portions of rivers, intermediate lines are another option. Full-sink lines are almost exclusively used on lakes to get your flies down deep and keep them there throughout the entire retrieve.

Wrapping Up

As confusing as fly lines can be, you’ll clear a lot of your questions up by going into the process with a clear goal in mind. Are you outfitting your 9′ 5-weight that you use for nymphs, dries, and streamers? An all-purpose line is probably best. But if you’re looking to pair your fast-action 3-weight with the right line for high-country fishing, then a true-to-weight line with a shorter head could be a great choice.

If you clearly understand what you’re trying to get the rod and line to do together, picking the line becomes a lot easier.