How To Choose The Right Fly Line Weight? (Line Weights Explained)


How to choose the right fly line weight?

I hear this all of the time and you need to match your fly line weight to your fly rod and reel. If you have a 5 weight rod then you need a 5 weight reel and a 5 weight line. This will let your rod, reel, and line work together, so you can cast easier.

In this article, we will focus on the fly line and why it is important to choose the right fly line weight.

We will also discuss the factors impacting your decision to choose the right fly line weights for your fly fishing.

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fly fishing rod and reel with different types of fishing flies

What are Fly Lines and Its Components?

Many people will tell you that choosing a fishing line is not really important and you can select any line which is weightless and has a heavy lure but allow me to correct this fact for you. In spin fishing, you can have an average size fishing line but in fly fishing, the line is more important than the rod itself.

This is because, in fly fishing, the weight and energy are in the line as you cast it. So it’s imperative that you choose a line that is not worn out and is specially designed for fly fishing.

Apart from replacing the lines when they are heavy and rough, also consider other factors of a fly line. They are the core, coating, and taper of each line. Every one of these components affects the fly fishing line’s performance.

For example, when choosing the core of the lines, you should use monofilament ones in hot weather and multifilament’s ones for coldwater species. Many manufacturers use PVC for coating and vary the plasticizers in it to make a fly line more or less stiff.

A fly line’s taper is extremely important to fly fishing too. A taper is the varying thickness of the line coating. Some parts of a fly line are thick while others are thin.

It is done so to determine how the line will perform in a variety of conditions. For example for catching large fish, you need a line weight which is as close the fly as possible whereas for small flies you would need a long but delicate tip.

Then you have the line weight. Its rating is based on the first thirty feet of line. The lowest rating is assigned to the lighter lines and it goes up. We will discuss the line weights in detail in the next heading.

fly fisherman fishing in sea

How to Determine Fly Line Weight

As an avid fisherman when you go into the shop for buying fishing supplies you will notice that there are different varieties of fly lines, each having different weights. No need to be confused though, because the weight of the fly line is pretty simple to understand.

All manufacturers in the USA use grains to measure the fly lines. There are 14 grains in a gram so if a fly line says it is of 140 grains it means that its total weight will be around 14 grams. But this too is a hassle for many people so the manufacturers have adopted a pretty easy-to-understand scale system.

You will notice that there will be a scale view written on the pack of the line you will buy. The scale value runs from 1-15 and it is universally applicable so no matter in the USA or Australia if your line pack says 4, it will be of the same weight.

You might be wondering why knowing this information is important. You see, the weight of the fly line is directly related to what you are fishing for.

So if you are aiming for a trout and choose a fishing line weight that says 4, you are in for a big surprise. A sad surprise actually because the probability of catching a small fish with a big line weight is near to zero.

Thus, it is helpful for you to know what type of fly line weight will work best in particular circumstances.

close-up fly fishing rod and reel with fly box in background

Why Matching the Rod and Line Weight is Important?

The big mistake anglers make when purchasing a fly fishing line is not matching it with the fly rod. Both are integral components of fly fishing and if they do not complement each other, chances are that it will ruin your fly fishing experience.

There are two ways to go about making purchases. First, consider what you are planning to fish for the most. Most species require a distinct rod and fishing line weight which we will discuss in detail in the next heading. When you have decided on the species you are going fishing for. Then buy the fishing rod and fly fishing line accordingly.

If you already have the rod, and just want the right line, look at the handle of the rod and you will find the line weight rating designated for the rod. Each rod is designed to carry a correct line weight for that rod. That line weight will cast best with the rod.

For example, if the rod has 6-7 labeling then it means that you need to buy a 6 or 7 weight line and it will work best with that rod.

Matching the rod and line weight is extremely important. Without this, your fly fishing system will be imbalanced and your casting will be affected. There is a balanced relationship between the rod and the casting line and these results in casting power for you.

When you pick up the line from the water, the line loads the rod by adding weight to it so that you are able to flex it fully. Then when you properly cast it, the flexed rod will straighten out and your line will drive forward.

So when you are shopping for line weights, just match the number with the line rod and you will have a balanced fly fishing system in your hands.

fly reel with orange fishing line

Things to Consider when Selecting Fly Line Weights

As we have established this before, fly fishing is different from conventional fishing because we use artificial flies in it. In conventional fishing, the weight of the lure carries out the line so you do not really need to worry about fly line weights but in fly fishing, it is the opposite.

As artificial flies have low weights and densities, the weight of the fly line helps to cast it.

Besides matching it with the rod and reel weight, selecting the right fly line weight depends on different factors. Let us look at them in detail.

Type of Water

In general, fly fishing line weights that are smaller in number from 0-3 are used in small streams and pond where fish are generally small and lightweight.

Fly line weights in the 4-8 categories are used most commonly in freshwater fishing targeting a variety of fish species.

Finally, the weights 9-15 are heavier so they are used for saltwater fish species like tarpon, trevally, and tuna.

Prevalent Weather Condition

If you are a lucky angler, you will be met by perfect weather conditions every time you fly fish but this seldom happens. Weather conditions are an important consideration you have to take while selecting fly fishing lines.

If you are going out in a windy environment, where you have a fear of your casting being disrupted by these high-powered winds, choose a fishing line that is on the higher side for example 6 and upwards.

Along with fly lines that are overweighted, heavier and faster action rods will help to cut the wind and allow you to turn your bugs over more efficiently in the wind.

Fly Size

If you are only fishing tiny flies, you should stick with the smaller fly line size 4. If your flies are larger go for sizes that are heavier like 6 to 8. Usually, shopkeepers will recommend you a 5 fly line which is the most popular trout line size and will cover all your bases.

Fish Size

When it comes to selecting fly line weights, the most important thing to consider is the type of fish. We have already mentioned that fly line weights come in sizes in a range from 0 to 15.

Each line weight is designed to catch specific species of fish depending on their weight and skills in the water.

Some fly fishers do well with just one fishing line weight and rod and catch pretty much everything in the water. But as you try new fly fishing skills or visit different areas, different fishing line weights might be better for you.

Here we have divided the fly line weight according to different species of fish.

fisherman holding fly fishing rod

How Many Fly Line Weights are Available?

Generally, worldwide fly fishing line weights are available on a scale of 1 to 15. 1 represents the lightest of the weight and 15 are the highest. In other words as the line weight increases, so does its ranking too.

Line weights are easy to select if you have already made your rod and reel purchase since they should match. Some manufacturers will tell you that it is completely okay to buy a line weight which is a rank higher or lower than the rod but if you want complete efficacy and efficiency in your fly fishing, match the line, rod, and reel exactly.

Fly Line Weight 0 to 2

These are the lightest weight lines, therefore, they work best for the smallest and quietest of fishes. Usually, they are not used for day-to-day fishing as it quite rarely happens that you encounter such small size of fish.

Species that come under this heading are all panfish, very small trout or in some cases, you can even fish for larger trout in tiny streams. But the weather conditions should be ideal.

Fly Line Weight 3-4

This fly fishing weight line is primarily made for trout. It will work best with mostly all sizes of trout except the larger ones. For panfish too, this weight can be considered.

It cannot be used on trout that are in large bodies of water but will work for those that are present in small or midsized streams, creeks, and ponds.

Also, make sure that you use it in areas where longer casts are not needed. For a general all-purpose freshwater line fishing, consider using these weights.

Fly Line Weight 5

Also known as an all and all trout fly line weight, this fishing weight is ideal for people who are into trout fishing. It will work for virtually all trout fishing situations.

It might also work on small fishes in ideal wind situation but it will not be as much fun as you will have when you use a lighter fly line.

Another type of fish with which you can work with this fishing line weight is smallmouth and largemouth bass in rivers which are generally smaller in size.

Fly Line Weight 6-7

These line weights are meant for larger trout and bass in freshwater as they offer the widest selection of lines and tackle. Do not try to use these for tiny trout and panfish.

This will be overkill as the rigs will be stouter and it will take a lot of effort for you to catch smaller fish. These are better for catching larger and more powerful fish like Salmon, Carp, Grayling, Bonefish, Redfish, and Steelhead.

Fly Line Weight 8-9

These are also called stouter lines and are meant to be used for big fish and in larger bodies of water. They are in a higher weight range so they are able to carry large flies.

In windy conditions, these rods also work best. Because of heavier weights, it can cause you casting fatigue as it requires more effort.

Generally, they are considered to be all-purpose but towards the heavier side of fishing. If you are saltwater fishing go for these lines as opposed to the lighter ones.

The fish you will catch through these lines include largemouth bass, carp, steelhead, salmon, northern pie and muskie, bonefish and redfish, striped bass, peacock bass, and false albacore.

Fly Line Weight 10-12

These line weights are generally associated with saltwater fishing where heavier fishing is needed. By heavier fishing we mean a sum of large fish, big flies, and windy conditions.

As these all factors come into play they demand more energy from the line, therefore, a lighter line is not suitable here.

Fish associated with this type of fishing are large carp, northern pike and muskie, striped bass, golden dorado, peacock bass, salmon, and false albacore.

Fly Line Weight 13-15

These lines are the highest in fly line weights and are generally used for saltwater species that are largest in both weight and size. Most fly fishers will not need these lines as they are reserved for people who are looking into a physical fight with fish.

Species that you can catch with these are huge tarpons, marlin, sailfish, bluefin, mahi-mahi, tarpon, roosters and giant trevally.

fly fishing rod and reel and caught sea trout

Fly fishing may appear to be easy but once all these details get involved, it kinds of becomes complicated and confusing for the angler. Just visit a store and you will be bombarded with a ton of color, sizes, weights, and numbers.

Yes, there are different sizes and types of fly lines and each of them works best in various different fishing situations. But after reading the above article, you will be clear about line weights, and how to choose them correctly.

Remember, as you become more experienced with your rod and different fishing situations. Then you will yourself come to know when you need a heavier or a lighter weight line. So continue fly fishing and enjoy this sport to the maximum.

Bob Hoffmann

The author of this post is Bob Hoffmann. Bob has spend most of his childhood fishing with his father and now share all his knowledge with other anglers. Feel free to leave a comment below.

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