There are three important choices to consider when choosing the right leader for fly fishing. They are the length of the leader, and the size of the diameter of the butt section and diameter of the tippet (or level portion at the end of the leader).
Three factors determine what length leader to use: the water condition, the type of fly line used, and the fish to be fished for. Sinking lines are nearly always fished with short (3-5 foot) leaders so the line can sink the fly more quickly and remain lower in the water column for a longer period of time. Floating lines are almost always fished with leaders from 7-12 feet long. The shorter leaders are used when water conditions are murky and make visibility poor or when water speed or turbulence require that fish be more opportunistic. Longer leaders are required when the water is shallow, very clear, or moving slowly or even still. Simply, the more a fish can scrutinize the fly, the longer the leader needs to be. Species are also a consideration. Bass and panfish are normally not very line or leader shy and can be fished with shorter leaders. Trout, on the other hand, can be very selective and wary. Longer leaders (9-12 feet) are important when fishing for spooky fish in low, clear water. These fish are often very line-shy and the line must be kept away from the fish by using a longer leader.
For a smooth transition from fly line to leader, it is important that the butt section be the right size. Leaders with butt sections that are too small or too large a diameter will tend hinge, jerk, or fail to lay out smoothly. In general, leader butt diameter should be approximately two thirdsthe diameter of the tip of the fly line. For normal trout fishing, leader butts should be .019-.023”.
Tippet sizes are usually described in X's. The X size of a tippet describes the diameter of the tippet as it relates to a scale of "11". This inverted scale is much like a wire guage scale. As the size of the tippet gets larger, the X rating gets smaller. For example, a 0X tippet is .011" in diameter. A 5X tippet is .006" in diameter... the X and the size in thousanths of inches always add up to 11.
Small flies require small diameter tippets and larger flies require larger tippets to work properly. In general, the size of the fly divided by 3 gives a good approximation of the “X” rating of the tippet. For example, a size 12 fly is normally fished with a 4X tippet and a size 18 fly is commonly tied to a 6X tippet. For extra clear water and spooky fish, use one size smaller. For murky water or night fishing, use one size larger. The exception to this “Rule of 3”, is when fishing for large species. For example, while a 20 pound salmon might eat a size #12 nymph pattern that I can cast easily with a 6 weight rod and a 4X, 6 pound tippet. However, that salmon will need a stronger weight tippet strength to fight and land. So species size is also a condition.
Tippets are one of the more confusing aspects of fly fishing for novices. First, the word “tippet” refers to level monofilament. That’s all. Every knotless, tapered leader has a tippet of at least 18 to 24 inches. If you have chosen the correct diameter leader, you could tie a fly on and easily fish it right out of the package. However, as you change flies, break off, knot up… etc. the tippet section (once again, the level portion of the leader at the end) gets closer to the taper and thus can begin to get larger in diameter and it is difficult to recognize the diameter getting larger. So, most fly anglers will take a new leader and add 18 to 24 inches of tippet material to the original tippet right out of the package. This allows the angler to know when the tippet is getting shorter (as it approaches the knot) and replace it when it gets too close. This will also make your leaders last longer.
The “X” rating of a leader added to its diameter in thousandths = 11. (e.g. 5x tippet = .006” diameter)
Fly size divided by 3 gives approx. tippet size to use.
(e.g. size 18 fly = 6x tippet)
The purpose of a tapered leader is to make smooth transition from fly line to leader. Both knotless and knotted leaders are heavier at the fly line connection and lighter or thinner at the fly or tippet end. The tapering of the leader allows the leader to slow gradually. The gradually thinning leader is slowed by the friction of the air it is passing through. As we mentioned earlier, the diameter of the tippet end is determined by the size of the fly attached. This is because larger flies require greater energy to carry them through the friction of the air. Small flies need less energy to lay out fully at the target. Below is a general breakdown of how a leader is tapered.
A heavy part that ties to the fly line. (60%) The butt section is approximately two thirds the diameter of tip of fly line. (.020”-.025”)
A transition section that reduces size to tippet. (20%)
A fine portion of leader that ties to fly. ( 20%) The tippet should be approximately 18" to 36” depending on water conditions. To accomplish this, additional tippet can be added after the leader is attached.
Last, but not least, when in doubt, ask your local fly shop expert which leader is suitable for the fishing you will be doing.