The complicated hand tied leader formulas are unnecessary.
For hand tied leaders, I use a very simple leader formula that I got from Gary Borger. He has modified his Uni-body leader formula a bit from the original. I have the latest formula. You can google "Gary Borger Uni-body Leader" to read about it but the following directions will allow you to make your own. You must use Maxima Chameleon for this leader to work. DO NOT SUBSTITUTE.
For the 4-6 wt rods that most of us use we need Maxima Chameleon (brown color) 0.020" (25 lb test) for the butt and 0.013 (12 lb test) for the transition. If you have 7 and 8 wt rods, buy some 0.024" (40 lb test) and 0.015" (15 lb test) Maxima Chameleon for the butt and transition respectively.
Each "base leader" without the tippet will have a butt section and a transition section made of the thicker and thinner Maxima Chameleon respectively. The transition section is ALWAYS 1 ft. long when finished. The transition section ends in a tippet ring and we will use a 3mm ring for the 4-6 wt rods. The tippet is added to the tippet ring. You can either tie the tippet to the ring or use a loop to loop connection.
The tippet ring allows you to change the tippet length and diameter easily without
shortening the 1 foot long transition section. You can eliminate the tippet ring and tie the tippet directly to the transition but you will lose the ability to quickly change the leader for nymphing vs dry fly fishing as explained below.
The butt section length varies with the total leader length. I include a perfection loop on my butt section which I use to connect the leader to the fly line with a loop to loop connection.
For a 9 ft leader the butt is 5 feet long (including the perfection loop) and the transition is 1 ft. long for a base leader length of 6 feet. Then add a 3 ft long supple tippet section and you have a Uni-body George Harvey style dry fly leader. For longer leaders, lengthen the .020" Maxima Chameleon.
For nymphing, Gary uses the following formula. Butt section is 4 ft long and transition is 1 ft long for base of 4 feet. There are two tippet sections. The top tippet section is 4 feet long. The tippet diameter depends on the nymph size. Use 0X for size 2-8, 1X for size 10-14 and 2X for size 16 and smaller.
Tie a 2 mm tippet ring to the end of the upper tippet section and then tie a second 12" section of tippet to this tippet ring. For the diameter of this lower tippet section, divide the hook size by 3. So for a size 16 fly you would use 16/3 = 5X tippet. Place your spit shot above this tippet ring. You can also place a dropper with a second fly on this tippet ring if you want to use dropper rather than tying a second nymph in-line with the first.
You can convert from a nymphing to a George Harvey dry fly leader by changing the terminal tippet design between dry fly and nymphing set up. I keep the various nymphing sections with the second tippet ring coiled and held with a bread wrapper wire tie in separate small zip lock bags. I do the same with the various dry fly tippet sections.
Each front end of the tippets have a perfection loops so I can swap them out with a loop to tippet ring connection. With this system I can quickly to go from a nymphing rig with the proper tippet size to a dry fly rig with the proper tippet size and back again.
You will notice that the 9 foot leader has a 5 ft butt section and Gary's nymphing leader has a 4 ft butt section. I use the 5 ft butt section leader for both dry fly fishing and nymphing. I find the 5 ft works fine for nymphing, and I want a longer leader for my dry flies so I have less change of spooking the fish.