Flies and Weights

by | Jan 24, 2021 | 13 comments

**NOTE** This is Part Four in a Troutbitten Short Series about weights and measures. You can find the full series at the link below.

READ: Troutbitten | Category | Know Your Weights and Measures

You can fish your whole life without thinking specifically about the weight of the flies on your line or their resistance to the air and water. You can also obsess about the details of your rig to the point where too many unanswered questions become obstacles — until you’re paralyzed with uncertainty.

Knowing your weights and measures and understanding how they interface starts with a simple awareness of things like leader length, material diameter, fly weight and distance to the target.

By considering the composition of the rig in your hands, questions form. Is the tippet diameter thick enough to turn over a #12 Parachute Adams? You must fish it to find out. It’s the only way.

What follows is the final installment in the Troutbitten short series, Know Your Weights and Measures. This finale focuses on the flies. I’ll provide examples of my flies and solutions below, but you must go into your own fishing with an open and curious mind. Because your fly rod, line, leader, tippet, casting stroke, river and water conditions are different than mine. I’m sure of it.

The distance from your target and the length you are casting is a knowable stat. And understanding that you are tight lining a nymph at twenty-five feet, for example, is an easy bit of knowledge to factor in. Things get more complicated when considering leader composition, but balancing power and turnover with length and material stiffness gets you out of the starting block.

So now, with some understanding of the accompanying elements, let’s think about the flies.

Photo by Bill Dell

Fly Size and Material Resistance (Dries)

Fly size is basic knowledge that most anglers pick up quickly. Not only is it easy to communicate to fellow anglers that trout were taking a size #14 CDC Caddis this morning, we also learn what tippet diameter and length matches with each fly. (5X nylon is a good start with that #14 caddis.)

Knowing these stats makes the next adaptation easier . . .

Hours later, the action changes when Hendricksons start popping through the surface. Rising trout suddenly ignore the caddis, so it seems a #14 Hendrickson in a parachute style could be the ticket. The fly size here might be the same as the morning caddis, but the material resistance differs greatly. A parachute style grabs the wind and holds the fly back as the casting loop unfolds, while the tent-style, v-wing of the caddis cuts through the air. Tippet adjustment is therefore necessary to get the same turnover and the same s-curves built into the leader, resulting in a continued drag-free presentation and more trout at the end of the line.

READ: Troutbitten | Dry Fly Fishing — The George Harvey Leader Design

With the Parachute, I’d likely shorten the 5X about a foot, then cast it to see if the change worked as expected.

Later in the evening, when trout find the Blue Winged Olive spinners, I might cut the 5x back another foot and add three to four feet of 6X nylon to cast the small olive spinner that has very little air resistance.

Importantly, it’s not just the size of the fly we must consider. It’s how the fly cuts through the air on delivery. And that material resistance matters in the water just as much as it does in the air. Let’s get to that . . .

Fly Size and Material Resistance (Underneath)

A Perdigon is the modern example of a nymph with limited resistance. Having no dubbing, chenille, hackle or legs to slow its descent, a Perdigon slices through the water column better than any other fly in my box. But sometimes, such a fly is not the best choice. And I often use Walt’s Worms, with their shaggy dubbing, as a slower-dropping option to match the size and weight of the fly I want to use.

Streamers should be given similar consideration. The deer hair head on my favorite Bunny Bullet Sculpin does not slice through the water. Instead it pushes water ahead of it on each strip, each jig or pulse. By contrast, a Half Pint streamer, in the same size, cuts through the water more than it pushes. It swims differently, and this contrast can literally be felt in the rod hand.

Material resistance vs weight is another balancing act on the water. Consider again the Perdigon vs the Walt’s. Without changing anything about my leader or presentation, I know the #14 Walt’s will sink at the same rate as the #16 Perdigon, from my fly box. And when I want to be deeper, quicker, I can choose a heavier fly or one that cuts through the water with ease — sometimes both.

We must change flies with size, weight and material resistance in mind. And just like the other weights and measures in this series, there is no substitute for experimentation on the water. Trying things for yourself is the best way to gain knowledge. Test without bias. And often, the results are surprising.

Photo by Bill Dell


I’ll focus here mostly on the weight of the flies, because I choose beadhead and weighted flies most often, for the extra contact and strike detection when no split shot is involved.

But this discussion translates also to drop shot rigging and standard split shot rigging. I do both on a regular basis. And there are some flies in my box, like eggs, worms and cress bugs, that just fish better for me without built-in weight. Sometimes the freedom of motion permitted to an unweighted nymph is more attractive and productive than the extra contact of using weighted flies.

READ: Troutbitten | Split Shot vs Weighted Flies

Knowing the weight at the end of the line is an excellent way to take the next step as an angler. And though it may seem confusing at first, thinking about weight quickly becomes as natural as knowing the hook size.

I use centigrams because it’s easiest for me, but some anglers think in grains instead. Ounces are not a good choice for fly fishing weights, because the increments aren’t small enough. (I don’t know anyone who wants to split fractions and think in 64ths out there.)

Some anglers choose to tie their #16 nymphs in multiple different weights, with various bead sizes. But my approach is simpler. Most of the #16 beadheads in my fly box are about 12-15 centigrams, so I round up and think of my #16’s as 15 cg. My #14’s are 25 cg, and so on. This system works well for me, because the bigger flies in my box are also heavier. It’s a simple approach that I’ve come to after trying other systems.

I can fine tune the weights because I use lead wraps behind the bead head, usually to about mid-shank. Here is my chart for nymphs:

Hook Size, Bead Size, Lead Size (wrapped to about mid-shank) and the resulting Fly Weight

Understand that the chart above is based on the hooks I use and the way I tie flies. The weight of your own flies may be quite different. There are some exceptions in my fly box, as well. For example, I tie my stoneflies and Polish Woven nymphs about 10 cg heavier than the chart above.

Additionally, here’s are the weights of the split shot that I use:

#1 30 cg
#4 20 cg
#6 10 cg

An advanced angler knows the weight required to get an excellent presentation in the target zone. My own understanding started by buying an inexpensive gram scale. But it took a while before I could look at a piece of water and think, “I need fifty centigrams here.”

This is the affordable AMS-100 gram scale I’ve used for ten years or more.

** Buy AMS-100 Gram Scale HERE to support Troutbitten **

So, if I’m fishing a #12 stonefly, and I’m getting great drifts with no action, then I may want to try smaller flies. And I know I can change to a pair of #14’s but still have the same sink rate. Likewise, while fishing two #16’s in a gliding flat, I may swap out to a single #14 as I move into pocket water, but I’ll still maintain (nearly) the same weight. Alternatively, I may clip the #16 from the tag and add a #6 shot five inches up from the point fly.

This is the direct advantage of knowing your weights. Fly changes become more deliberate and less experimental. Efficiency improves, as does your confidence to read water and the ability to fish it well.

But knowing the weight at the end of the line is also a great advantage when considering the rest of the rig in your hands.

Weights and the Other Stuff

On my standard Mono Rig with an upstream tuck cast, I can fish 25 centigrams at 25 feet with negligible leader sag. But fishing beyond that distance requires either more weight, a thinner leader or a suspension tactic.

Knowing these stats makes fishing easier for me. I’ve tested weights, distances and leaders enough that I have confidence in the conclusions. I know what is possible at 25 feet, and I know how to adapt to get a good drift at 30 feet.

It’s all interactive. Choosing five feet of 6X instead of four feet of 5X requires less weight in the flies to get down. And the material resistance of a large, leggy stonefly helps hold the fly in the strike zone once it’s there. The stone counteracts the sag of a thicker butt section in my euro nymphing or tight line setup, while that thicker leader also provides more turnover power at distance. The best anglers understand that there are many different ways to accomplish the same thing.

Your Stats

Knowing your weights and measures is about understanding how to balance the elements of your fishing rig. It’s a give and take. But it’s up to you to first know what is being balanced. It’s the design of the leader, the weight of the flies, material resistance and distance. Put numbers to these things, and know your stats.

Then, begin to form an understanding of how to adapt these elements to achieve the necessary balance and change the outcome — to cast a tight line further with less sag or to cast a dry line closer with more s-curves.

Think of the principles covered in this Troutbitten short series as basic knowledge, as theory for understanding more about the way each element in your rig compliments the others. Then get out there and ask some questions of yourself. Learn a little each time, until you eventually piece together a system of weights and measures. And have fun out there.

Fish hard, friends.

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Enjoy the day.
Domenick Swentosky


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Domenick Swentosky

Central Pennsylvania

Hi. I’m a father of two young boys, a husband, author, fly fishing guide and a musician. I fish for wild brown trout in the cool limestone waters of Central Pennsylvania year round. This is my home, and I love it. Friends. Family. And the river.

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  1. Thanks for another great article. I weighed my nymphs when I started euro nymphing so I could understand how much they weighed compared to split shot that I used prior. I also wrote the weights in grams using a sharpie in my fly box and organized based on that. I haven’t done in while so this is a good reminder to go through my fly box again reweigh and reorganize based on weight.

    • Good stuff.

      I think the most important thing about all this is to bring it into the other weights and measures discussed above: distance and leader design, like diameter and stiffness. For me, the point here isn’t just that it takes 25 cg to get down in a certain piece of water, but how it all works together in the whole rig.


  2. Hey Dom, yet another great helpful article.

    One of the rivers I fish is quite heavy water, it has an average flow of about 27cubicmeters / sec. A single fly # 10 hook with a 4.50 mm bead and tuck cast gets down fast but the fish generally feed on smaller morsels free swimming caddis and mayfly nymphs. So the single heavy point fly seems the least productive.

    Given the mass required to get down fast what do you think might give the best least drag subsurface presentation. Heavy point fly with 4.5 mm bead and a lightweight fly without a bead on the dropper or two weighted flies of about equivalent weight of the single heavy point fly?

    I’ve “experimented “ using both rigs with mixed results in both pocket water and seams with relatively even flow. Your thoughts,ideas suggestions most welcome

    • Hi AJ,

      In that case, I tend to fish a drop shot rig. I don’t care for extremely heavy “sacrificial” flies if they don’t catch many trout. So I will use shot for the weight and then tie on unweighted or reasonably weighted flies above it.

      Make sense?


  3. As a rookie angler my head is usually spinning and this series on weights and measures is definitely overwhelming from where I sit today. However, I really appreciate the lesson that if consistently approached methodically and deliberately, one can start to make sense of it all. Thanks for the info, looking forward to reading the entire backlog of posts.

  4. Dom, thanks again for another great article. I noticed your weight changes didn’t quite match. For example, two #16s based on your formula would be 5CG heavier than one #14. Is that because you’re accounting for the added water resistance created by the added nymph or is it just not important to be that exact?

    • Hi Jason,

      That’s right. There’s a bit of compensation going on with every change and adaptation. Two 16’s do have more resistance than a single 14. And they will often sink a bit slower because they are probably in slightly different currents, as well.

      Also, 5 cg is nothing to obsess about, either. It matters, yes. But the other factors at hand should never be forgotten.

      Many of the comments on social media for this article seem to be just looking at the scale — the weighing of flies — as the main point. But it is not. The thrust of this weights and measures series is to understand how each element affects the others. It’s about finding a balance. It’s about knowing what happens by choosing a fly that is twenty centigrams heavier — how that counteracts some of the line sag from a butt section that is, perhaps, .005″ thicker.


      • So much to experiment with. Can’t complain about that! Thanks.

    • Yes indeed Dom good idea thank you

  5. Have you considered measuring the combined effects of weight/mass and hydraulic drag on sink rates. It would be pretty easy to do and could include an attached tippet for correct posture while sinking. Units would be millimeters per second. Just be sure to keep water temp, water depth, release point, and tippet material constant. The only way to provide a fair comparison that matters.

    • Hi Rick,

      No thanks. I’ll leave that to you. I believe there are just too many immeasurables and variables there for me to be interested.

      “The only way to provide a fair comparison that matters.”

      I disagree. That’s why I wrote the article. I’m not the only angler to believe there’s value in knowing how much weight we are slinging around.

      Also, you are focusing merely on the sink rate. That’s not the only point here. The Weights and Measures series is about the INTERACTION between all the elements. So knowing the weights matters more than just the sink rate.


  6. Are you using tungsten bead heads?


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Domenick Swentosky

Central Pennsylvania

Hi. I’m a father of two young boys, a husband, author, fly fishing guide and a musician. I fish for wild brown trout in the cool limestone waters of Central Pennsylvania year round. This is my home, and I love it. Friends. Family. And the river.

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