One of my students a beginner (casting rather well) recently had an outing casting from a boat. There was the eternal wind blowing and the boat moving and all that. But the main issue was that the leader was misbehaving and didn’t turn over. The caster was struggling to lay out the line and the leader straight. The caster had no control over the leader and fly, and never was able to lay the ensemble out straight

We all have been there at some point in our journey. Now, I did some sleuthing of the equipment. The rod, an old stalwart #9 Sage II was not the issue. The #9 fly line was a new correctly sized one – not the problem. Now, the leader turned out to be a 12‘long hand-tied affair with a butt section of 0.024‘‘. The fly used was a weighted (bead chain) streamer.

Length of leader

Long leaders (10’ or more) are frequently advocated by guides and experienced anglers. Yet, as the leader lengthens it gets to be much more difficult to cast. The savants forget those beginners will struggle with long leaders plus the wind and a heavy fly. The leader must work for the angler using it, and it makes no sense to use a long leader if it does not turn over. You are better off with a shorter leader that you can turn over and lay out straight. Even if a long leader is preferable, if the caster can’t make it work, it isn’t the right leader.

Butt thickness

My #9 bonefish fly line has a 0.040’’ tip diameter (have micrometer will measure). That diameter calls for the butt’s leader to be around 70% of the fly line’s diameter. 0.040 x 0.7 = 0.028’’ for the two to have comparable masses. Our leader’s butt was not terrible (0.024’’) but not optimal either. For optimal transfer of energy from the fly line to the leader, the masses of each at their juncture must be close to the same. And the longer the leader the more important it becomes that the butt is heavy enough.

Heavy fly

We all know that heavy flies can kick when we cast them. Heavy flies are usually on the big side too and will have more drag. So, using a smaller lighter fly, if possible, will help.

The caster’s ability

The idiot savants of casting can fling out just about anything – long leaders with big flies no problem. However, beginners can’t do that. We must always curtail our advice to the ability of the caster being advised.

My advice for beginners

Buy ready-made leaders and forget the advice of the experts they can tie their own leaders, but it takes experience to get there. Ready-made leaders are now high quality and thus you will have fewer knots (it takes experience to tie great knots). Pay attention to the butt thickness. Quality leaders will have the butt diameter printed on the info sheet. A very good bet is that anglers’ butts are too thin. If you can’t turn over your leader – it is too long and/or fly too heavy/big for your casting abilities. You are in the game with a 9’ leader and your preferred fly laid out straight – but not if you have a 12’ leader collapsed in a bird’s nest.

Your casting abilities at any time are what they are i.e., not a variable, but leader length, butt diameter, and fly can be varied to get the desired outcome. There is no need for self-inflicted wounds or unforced errors. It is difficult enough as it is.

Technical consultant: Bruce Richards

There are lots of companies offering their leaders. It isn’t practical to go through all of them. I choose to portray some of SA’s leaders simply because I know exactly, what I am getting when I buy those. The diameters (butt-tippet) of each leader is clearly stated. If the diameters are not stated, I will not buy that leader. All companies list the break strength and length.

We have defined the three parts of the leader. First comes the butt end, which needs to be 70% of the diameter of the floating fly line tip. The middle part then tapers, and the leader ends in the level tippet. The tippet needs to match the hook size to a degree. Modern commercial leaders have become fantastic. They are offered in various lengths, tippet/butt diameters, suppleness, and break strengths. You can find a leader for all your fishing needs from various companies. I strongly advise beginners to use the commercially available leaders at the outset. Mono has become much stronger over the years, and the quality of the leader material has improved. If anglers can’t find a leader that works for them – they need to fix their casting!

Ready-made leaders mostly come with a pre-tied loop on the butt end. When you use such a ready-made leader there is only one knot to worry about — the one for the fly. There are certain types of knots that work well for backing to reel, backing to fly line, fly line to the leader, leader to tippet, and finally tippet to the fly. The knot to learn first is therefore in the terminal connection category.

This site lists 34 terminal knots that you can use. There are undoubtedly many more. To tie the fly onto the leader, I use the classic Clinch knot and sometimes the Uni knot. It does not really matter which one you use if they are tied badly! Here again, the problem of choice rears its ugly head. So, which knots to choose? Actually, it does not matter much which type of knot you choose, just choose one for each job, and stick with it.

If you come to a fork in the road – take it (Yogi Berra).

Trout Leader

Trout Leader
Trout Leader

To give you an idea of ready-made leaders you can buy – let’s start with the Trout Leaders. It is simplest to display the information in a table. It is much easier to visualize that way.

So, 22 different trout leaders are available! You don’t really have to make your own. Below are pointers on which ones to use and when. Remember, for beginners the shorter leaders work best. As your casting improves you can cast longer leaders, but they are rarely required.

When and why would we choose a short or long leader? Usually the reason has to do with visibility. If the water is murky or it is night-time, very short leaders and heavy tippets work fine. If the water is gin clear, the sky bright and cloudless, the water calm, and the fish are biting, and enjoy great visibility (think bonefish, or trout), then you need a longer leader, and longer lighter tippet.

Seven feet six-inch leader.

1.         Short, powerful and ideal for casting big/heavy flies/fly. Just remember to open your loops when delivering the heavy load. On a windy day this leader can become a great trout leader. This length leader is the easiest one to cast.

2.         The butt diameter is the easy part – it needs to be 70% of the diameter of the level tip of your terminal floating line.

3.         The break strength is decided by the size of the fish, and the size of the fly you choose (#fly divided by 3 – indicates X size of your tippet).

Nine-foot leader.

1.         This leader length can be viewed as the standard-length leader. This length is my default and is practical in most situations. Just a tad more difficult to cast than the 7.5’ leader for a beginner.

2.         The butt diameter is easy – it needs to be 70% of the diameter of the level tip of your terminal floating line.

3.         The break strength is decided by the size of the fish, and the size of the fly you choose (#fly divided by 3 – indicates X size of your tippet).

Eleven-foot leader.

1.         This leader length can become useful in situations where the fish enjoy great visibility – clear water, mirror surface, sunny day. If the trout are finicky an eleven-foot leader places the end of the fly line further from the fish, which can become advantageous. However, those extra 2 feet will become much harder to cast for a beginner.   

2.         The butt diameter is easy – it needs to be 70% of the diameter of the level tip of your terminal floating line.

3.         The break strength is decided by the size of the fish, and the size of the fly you choose (#fly divided by 3 – indicates X size of your tippet).

Fourteen feet leader.

1.         For the idiot savants of fly casting, NOT to be recommended to beginners

Great Blue Heron
Great Blue Heron

Salmon, Steelhead and Seatrout

For Icelandic readers – steelhead is a seagoing rainbow. For American readers – seatrout is a seagoing brown trout (in British English). So, here we have five nine-foot leaders, and three twelve-foot leaders. It is enough for me. These anglers don’t use the X system, only worrying about the break strength of the tippet and the leader length. Nine-foot leaders are the standard. In low water situations and when the visibility for the fish is good, twelve-foot leaders are handy.

Salmon Steelhead and Seatrout Leader
Salmon Steelhead and Seatrout Leader


Here you have five different leaders to choose from and that’s plenty in my book. Break strength is the all-important factor. This crowd does not pay enough attention to the butt size of their leaders, but they should because the flies are often heavy, and you need optimal energy transfer from the fly line to turn the beasts over. However, these leaders have the optimal butt diameters.

Saltwater Leader
Saltwater Leader

The red thread for all the leaders above

I noticed, when looking at these leaders, that all these leaders have relative thick butts. By relative I mean in respect to the butt diameters I was used to using chasing trout in Iceland twenty years ago. The butt diameters are not a coincidence. This manufacturer knows the importance of matching the leader to the fly line likely to be used, and these leaders cast very well with the correct line.

You also have noticed the marketing “trout leader” “salmon leader” “saltwater leader” terms. These are all high-end copolymer nylon with a relative density of 1.2. They have no awareness and have no idea where they are. The fish don’t care what we call those leaders either. So, you can use them whenever, wherever you are fishing, if the break strength and diameters and length is ok. The leaders above are made to be used with floating lines.

Brown Pelican
Brown Pelican

Sunken leaders

When you are using lines that sink (sinking, sink tip, or intermediate clear tip lines) you do not need a long leader. Sinking lines can have a very heavy terminal end, plus are often used with quite heavy flies. These leaders work very well, but remember to change your casting. Sinking type lines should not be cast as floating lines. Open up your loops and minimize your false casting. On each forward cast lay the line down for an instant, then backcast and gradually shoot the line out. This type of leader can be used to an advantage with floating lines too. If you are casting a very heavy streamer you can use a four-foot leader to ensure that you can turn the streamer over. Floating lines with a clear floating tip do not need long leaders – this leader works well with such a line.

Sinking Leader
Sinking Leader

But which one ……………?

I have tried to explain the fundamental basics of how you choose your leader. When you understand those, you can choose which leader to use in the different scenarios you encounter. So, the answer to the question above is —– use the right one. Remember, that the leader you need to use is dependent on your casting abilities, and to a degree on the weather, too. In bad windy weather go shorter. If there is great visibility for the fish, then go longer but never exceed your casting abilities.

English consultant: My good retired neighbor Joe

Technical consultant: Bruce Richards

The leader is probably the most overlooked or misunderstood part of the fly casting system. It is impossible to do the subject any justice in one blog, therefore I will parse it out. This part covers various generalities on leaders.


Much is written on leaders in fly fishing. A Google search – “fly fishing leaders” – yields about 17,600,000 hits (0.91 seconds). That’s a lot to chew through, and if you missed the 11,111,00th you are in serious trouble. Some pieces are of course excellent, and others are less so. However, leaders are often made out to be very complicated, when they are not. Remember, the leader is a continuum of the fly line that happens to be clear. The front taper of the fly line tapers down to dissipate the energy of the cast, but should leave just enough energy to turn over the leader and the fly. That’s the leader’s function (dissipate energy – turn over fly) – there is no mystery. The standard leader is 9′ long, starts with a butt end, and ends after tapering, in the now thinner tippet end. That’s it – that all there is to it.


When ruminating on leaders, we must make clear, that they are caster dependent. The longer they get, the better you must cast, and the more delicate leaders require better casting. Casting is always a part of leader design. So, remember the leader you use must match your casting abilities. Those who recommend a certain leader, should also state for whom it is intended. If a leader is very long and delicate, it is for the idiot savants of fly casting, but they do not need any help for sure. Our recommendations are for beginners and average casters.

The leader you use trout fishing is also dependent on the general visibility of the day. A calm day with no cloud coverage and clear water, means good visibility for the fish, and calls for a little longer leader. On a dark rainy day the leader can be a bit shorter. The mass of the fly used is very important. Small dries can be cast with delicate leaders whereas a big weighted Wooly Bugger needs a much more powerful leader.

Bonefish released
Bonefish released


Some housekeeping before we dive into it. A commercial leader comes in one piece. The thick first part is the level butt, then we have the mid-section or the taper, and finally the level tippet. The leader starts out level, then tapers down, and then levels out again. As you change your flies the tippet or terminal portion of your leader gets cut, and the leader shortens. Therefore, you carry a spool of mono of similar diameter to the tippet, and tie in pieces to lengthen the leader again. Mono just means single stranded, but the term has drifted (languages do that) to mean nylon in fly fish speak. Fluorocarbon (also mono) is also used as tippet material, often just shortened to fluoro.

Tippet – The rule of eleven

The tippet material is loaded onto spools, and marked with its breaking test – 5 pound or 10 pounds, etc.- and the diameter of tippet which is far more important. Then there is something called X, for instance X, 2X or 5X stamped on the spool label. This X system is used to indicate the diameter of monofilament lines. This X denotation comes from the past like so much in our sport. Leaders were made from silk worm guts. The segments were then drawn through dies that shaved off a little bit every passage. 3X had been 3 times through etc. The higher the X number the thinner the tippet.

Now the standard is set so that 0X is 0.011 inches thick. Subtract the number prefix to the X from 0.011 to find the diameter of the tippet – for 1X we go 0.011 – 1 = 0.010 etc. Take the 2 numbers, add together = 11. Another way to explain this is to say the X rating plus the diameter in thousandths will be equal to 11. (5 thousandths (.005”) + 6X = 11. 3X + 8 thousandths (.008”) = 11). Now, the various sizes can be found in the table below. Of course the diameter of the tippet is also stated making the x system redundant but the “trouters” love it and therefore it stays. The “salters” only pay attention to the breaking test of their tippet when they should be paying attention to the diameter too.

X number and diameter

Mass or break strength

Tippet material has evolved and become very strong. Now for instance, you can get tippet material with 0.011” diameter that has an impressive 16 lb. break strength (diameter of “old tech” 16 lb. Mason Hard mono is 0.020″). Its density has not increased – it is still the same. The mass of such a piece of tippet is therefore smaller than the “older” tippet. However, the turnover of the leader is dependent on the MASS of the leader NOT the break strength og the tippet. Therefore, the diameter (better indicator of mass) of the tippet is the all important factor, not the break strength, when building leaders or adding tippet to a leader. We should emphasize that tensile strength of sections of leaders are unimportant EXCEPT for the tippet, the weak link. Pay no attention to the tensile strength of butt and taper, it will lead you astray, the mass/diameter rule is the important one!

Pay attention to your butt size

So, in the last blog (see below), I explained the importance of having a thick butt on your leader connecting to your fly line. Approximately 70% off the diameter of the tip of the fly line is the goal for the butt’s leader. We arrived at the 70% figure by dividing the relative density of the floating fly line tip or 0.85, with the relative density of 6/6 nylon or 1.2 – 0.85/1.2 = 0.70. This applies only to floating lines. The relative density of the tip of sinking lines is much higher. Therefore open up your loop to minimize the kick, when casting sinking lines. So, it follows that the meatier lines need leaders with thicker butts. You can easily measure the tip off the fly line with a micrometer. The butt diameters of ready-made commercial leaders is now generally of the right size.

Purpose of leader

What’s the purpose of the leader? To deliver the fly, and dissipate the energy of the cast. That’s best achieved by tapering the leader, insuring just enough energy to turn over the fly. Ready made leaders start level, then they taper down and level out again. If you are casting as hard as you can and can’t turn over the leader you need to shorten it and/or use a lighter fly.

The leader ends where we tie in the fly. Not rocket science exactly. But it is obvious that we can’t tie a very thick tippet to a small Collie dog. Conversely, we don’t tie a 3 lb. tippet to a monstrous ten-inch fly. Therefore, it is clear that the tippet size must match the hook size to an extent. You can also divide fly size by 3 and that’s your X size. Adjust up or down 1 size depending on conditions. The recommendation for the tippet size and hook size is more fluid than the recommendation for the butt size, but you’ll get the idea. As you bumble along you get a feel for the size of tippet to use with the various hook sizes.

Salmon released
Salmon released

Light lines can’t cast heavy flies

Some fish (bonefish and salmon for instance) take flies that could easily be cast with light rods. However, you do not want to deal with a salmon equipped with a four-weight rod. Same goes for bonefish. The bonefish flats are wind swept, and you just need heavier lines because of that. If the fight gets prolonged, a shark will eat the exhausted bonefish for sure. It is super important to remember that you can cast small flies with heavy gear, but can’t cast big flies with light gear.

English consultant: My good retired neighbor Joe

Technical consultant: Bruce Richards

The line kicks

When a fly line is cast without a leader it will kick. The caster loses his/her control over the fly line. If you doubt it stop reading now and try for yourself. …….. Ok, now you tried, and we can continue. The energy that usually propels the fly line, and straightens the leader, is still there, but now the energy has nowhere to go but back up the line, and the line kicks. Now, what happens when you cast a line with a leader? Voila, it doesn’t kick now. The energy in the line is now transferred (bleeds) into the leader. Of course, as all this is happening the energy of the cast dissipates because of the drag.

Enter physics

Moving mass (the fly line, leader and fly) is governed by a law of physics – the law of the conservation of momentum. It is a simple one, and for our discussion a useful one. When we cast a fly line and the loop starts to form, the rod leg of the line is stationary. The top/fly leg has all the momentum, but as it passes the apex of the loop and becomes the rod leg, it loses mass, but picks up speed. This increased speed is now dissipated by the drag (speed doubles – drag quadruples). At the end of the cast there needs to be just enough energy to turn over the leader and the fly. So, that energy needs to reach the fly. All explanations and theories of fly casting must be rooted in the laws of physics. If not, they are simply wrong.

Mr. Redfish
Mr. Redfish is caught with a heavy fly

Noticed the fly line speed up?

From the formula (p=mass * speed) it is easy to understand — when mass decreases speed must increase. You have probably noticed that the line sometimes speeds up at the end of your cast – well, pay close attention next time you cast, and you can see this happen. The energy of the cast is moved through the mass of the line, and it is obvious that the energy in the line must transfer over to the mass of the leader. That transfer works to our advantage if the mass of the leader’s butt end is about the mass of the terminal level tip of the fly line. If the diameter of the leader’s butt is approximately 70% of the level tip of the fly line, we are in the game. You noticed that I was writing about the mass of this and that, and suddenly I am using diameters. Well, the greater the diameter of the leader material the heavier it is (more mass). We have these diameters printed on the leader info sheet (if there is no such info don’t buy that leader), and the butt and fly line tip diameter are easy to measure with a micrometer (yes, I do that!). Therefore, it is now easier to use the diameters in our communication.

Angler’s leader butt is generally too small

I can guarantee that most fly anglers will use a leader where the butt diameter is too small, and does not match the tip of the fly line (70% is enough). There is simply insufficient diameter/mass in the leader butt to transfer the energy from the fly line. That is a sure way to lose energy, and then the leader does not have enough energy to turn over, and the fly lands on the top of the sorry pile of a leader. I know this well because I have been there. This is when the demon whispers into your ear – “son, that ultra-fast new fly rod is what you need.” Yes, yes, yes and you rush off and buy the ultra-fast ……. fly rod, but you still cast bird’s nests.  The road mostly untaken runs through coaching and practice. It is galling that such a simple remedy exists, i.e. just use a leader with enough diameter/mass in the butt section to turn over your leader and fly. However, folks generally do not understand this principle and suffer accordingly.

Running of the Bull Reds
Bull Red – when you pay attention you are rewarded.

As the energy rolls along the fly line to the leader, the leader is dissipating energy (as it speeds up, the drag increases). Now, by having a tapered leader you also immediately realize — as the mass decreases the speed must increase (law of conservation of momentum), and thus we have generated enough energy to turn over even a heavy fly. It’s now obvious that we can cast a small fly with a longer leader than we can cast a heavy fly. It follows that sometimes by just shortening your leader, you can now turn over that heavy fly causing you so much trouble on your last trip.

Enjoy it more

Baz with Mr. Red
Capt. Baz is certainly enjoying this red

There is no absolute need for you to understand the physics of fly casting to enjoy the sport. However, you certainly will enjoy your sport much better when your cast improves, when you can turn over big heavy flies by paying attention to the butt end of your leader.

Morale of the story

So, the morale of this story is always to use a leader, whose butt’s diameter is somewhere around 70% of the tip of the fly line. This will ensure optimal transfer of energy from your fly line to your leader, improving your cast, and ensuring turnover of heavier flies.

What to look for

A note on leader purchase. Leaders are sold in small packets where you will probably only see indicated the breaking strength, and perhaps some X designation (salt anglers do not care about the X denotation). However, the X designation is useful for trout fishermen for diameter, and relates to suppleness, and strength too. Armed with this new advice of matching the butt of the leader to your fly line, you should be looking for Length, Tippet Diameter, Butt Diameter, and Break Strength. If no such information is divulged, do not buy the leader. (see picture below)

One company’s great info sheet.

English consultant: My good retired neighbor Joe

More on leaders from my web book

Here is a lecture on matching a fly line and a fly rod.

Technical consultant: Bruce Richards