How to Choose a Fly Fishing Line

Headed out for rising trout? Chasing stripers in deep water? Here's a primer on choosing the right fly line
Joe Cermele Avatar
how to choose fly line
Choosing the right fly line is essential to get the most out of your fly rod. Joe Cermele

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To the uninitiated, choosing the right type of fly fishing line can be rather daunting. Unlike conventional rods and reels, which rely on the weight of the lure or rig to cast effectively, a fly rod has to be paired with the right line to deliver the fly properly based on the task at hand.

The first step in choosing a fly line is understanding the weight system. Fly rods are designed to cast lines of a specific weight, which means that a 5-weight rod will work best with a 5-weight line, and a 10-weight rod will work best with a 10-weight line. (Fly lines are measured in grains, and each line has a standard grain weight set by the American Fly Fishing Trade Association.) If you match the wrong weight fly line to your fly rod, it simply won’t balance and, therefore, won’t deliver.

With this correlation in mind, you also have to consider the type of fly line that you need. Visit any local fly shop and you’ll find dozens of specialty lines on the wall. These all have their time and place, but for most anglers, the decision boils down to three main types of fly line. By understanding how these different lines function, you’ll be much better equipped to select the right fly line for your home water.

Floating Fly Line

Best For: Dry flies, nymphs, poppers, shallow-water streamer fishing

If you were to peg a “standard” fly line, it would be a floating line. After all, fly fishing was originally developed as a method of presenting flies that mimicked bugs and other small critters floating or swimming on the water’s surface. This means that traditional methods of fly casting are based around the behavior and functionality of a floating line.

Floating lines come in different tapers, with the most common being a weight-forward taper. This is designated by WF on the packaging, and it simply means that roughly 90 percent of the line is a thin diameter, while the remaining 10 percent at the “head” of the fly line (nearest the fly) tapers into a thicker diameter. The thin section is referred to as “running line” and provides little function in terms of casting. The thicker front end is what helps generate line speed and distance. This helps the line unfurl or “turn over” so that the leader lands in a straight line and the fly lands on target.  

Some folks who are new to fly fishing get caught up in the misconception that a floating fly line is useless if they intend to use patterns that are not presented on the surface, such as nymphs or streamers. This couldn’t be further from the truth. Most fly-fishing pursuits occur in less than 10 feet of water, and by simply adjusting the length of your leader, you can effectively fish subsurface flies in most scenarios with a floating line. They are the most versatile lines for a wide range of applications, and it’s only when you begin dabbling in niche fisheries and presentations that you should consider anything other than a weight-forward floating line.

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Sink-Tip Lines

Best For: Large streamers, large rivers and lakes, saltwater fishing

Sink-tip lines are a mashup of floating and full-sinking lines. The running line floats, but in lieu of a fat, tapered floating head, these lines feature a 10- to 30-foot head of sinking line. Choosing the perfect sink tip for the task at hand, however, is a bit more complicated than grabbing a weight-forward floating line.

The weight of a sink-tip line translates to a sink rate, which is typically provided on the package. To give examples, a line marked 3IPS will sink at a rate of 3 inches per second, while a 7IPS sink-tip line will drop seven inches per second. (These ratings are based on the line’s performance in still water, as they don’t take current into account.) It’s important to understand these sink rates when matching the right line to the water you’re fishing.   

Sink-tip lines are used most by devout streamer anglers fishing for trout, muskies, pike, and various saltwater species. What’s key is that these lines are used less to get a fly to a specific depth than to simply get a fly under the surface as quickly as possible and help combat the inherent buoyancy of larger, bulkier flies used for big predatory species. Sink tips are especially useful in moving water, as you’re often casting at a small target (like a seam behind a rock or short eddy) and you want your fly in the zone ASAP. One perk of sink tips is that they’re typically easier to cast than full-sink lines, as the weighted head provides the same oomph as a weight-forward floating line.

Full-Sink Lines

Best For: Targeting fish in depths greater than 15 feet

Full-sink fly lines are specialty tools. In all my years on the water, I’ve only found myself in scenarios that called for them a handful of times. And if I’m being honest, the smarter thing to do in most of those instances would have been to pick up a spinning rod because it would have been far more efficient. Still, these lines exist for a reason, and if you must get a streamer in front of a lake trout in 30 feet of water, you’re going to want one.

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Although modern technology has advanced full-sink lines over the last ten years or so, they’re still heavy and a bit cumbersome to cast. All 90 feet of the fly line features a weighted core, and many are the same diameter from end to end, which means there’s no tapered section to help the line shoot easily through the guides.

Should you need a full-sink line, keep in mind that they will not sink in a straight, flat line. The fly and leader will provide just enough resistance that the line will bow in the middle, creating a slight “U” shape between the fly and the rod tip. As you’re retrieving the fly, it becomes necessary to factor in this sag. If you strip too slow, a hit may never translate to the rod tip. And if you do feel the take, you’re going to have to strip extra fast and hard to get that bow out and achieve a solid hook set.