Fly size vs. line weight

Salmologic’s G&G Recommendation System

Fly fishing tackle may consist of the best and most expensive single parts, but if rod, reel, line, leader and fly do not work as a unit, the quality of the individual part is basically unimportant. 

Salmologic rods, reels, lines and leaders will be recommended in grams and grains (G&G system) thereby enabling the customers to make the right decisions when he/she is setting up their tackle for fishing. The fact is that every line class has its own fly sizes and it is therefore important to purchase the right line weight according to the fly sizes you normally fish with.  

Let me give you an example: If you normally fish for sea trout or salmon in a low glassy river and you use double hook sizes between 8 and 12, or with small cone head brass tubes, then a really good line weight, to match those conditions and fly sizes (in my opinion) would be around 20 grams/308 grains.

This Nordic rod is prefectly loaded with a 16 grams/247 grains head – on our products you will not find the confusing AFTM system, just the logic G&G system.
This Nordic rod is prefectly loaded with a 16 grams/247 grains head – on our products you will not find the confusing AFTM system, just the logic G&G system.

To make sure your tackle is well-balanced, you would then need a rod that loads perfectly with 20 grams and a leader with the correct mass to turn over that fly size and, even more importantly, balance the speed between the upper and lower line in your loop going forward. Believe me, the leader is the most important part of your equipment and it is completely overlooked.

We, at salmologic, know the physics and the dynamics in a fly cast and how everything should be combined together. Therefore, we have decided against using the confusing AFTM system. Instead, we use what we call our G&G system – a Grams and Grains system – because it makes sense. This is the only sure way that a fly fisherman has a chance to make the right decision when assembling his/her gear. Nothing gives an angler a better start in fly casting/fly fishing than the confidence that the tools he/she is using are actually perfectly “made to match” and balanced correctly.

We take the guessing out of the gear. We empower the customer to match their setup correctly because we know how amazing fly fishing is, and how easy it is when the setup is perfect. Using our G&G system is most definitely a step in the right direction for everyone.

Tight lines
Henrik Mortensen


Line weight versus fly size

The starting point is always to consider which type of fly you would need for the water you are fishing. When you know which size of fly you are going to put on the leader, then you will also have an idea of the line weight needed. For example, a large and heavy fly takes a heavier line (which equals a higher line weight) in order to be able to cast and present the fly properly. The following table is a list of different line weights and what I believe are the fly sizes that match those line weights for trout and salmon fishing.  

The weight listed below is the loading weight for any of our line systems. The weights listed are the actual weight for a shooting head, or the weight of a belly if it is a weight forward line.

Compared to the Logic nylon leaders, the Logic coated leaders enable you to cast bigger flies and also allow you to have more control over which water column your fly will be fishing. The recommendation below only takes Logic coated leaders into account. However, do not count or include the leader’s actual weight as part of the loading weight – because it is not! If I had to go into more detail here, this recommendation would turn into a long and detailed article, so please just take my word for it.

The recommendation of fly size versus leader length when using Logic nylon leaders can be found under the Logic nylon leaders page on this website.

  • 12g/185gr – size 12-10 single hooks
  • 14g/216gr – size 10-8 single hooks.
  • 16g/247gr – size 10-8 single- and double hooks.
  • 18g/278gr – size 8-6 single- and double hooks, or ¼ inch brass tubes.
  • 20g/308gr – size 8-6 single hooks, size 10-6 double hooks, and ¼ inch alu or brass tubes.
  • 22g/340gr – size 6-4 single hooks, size 10-6 double hooks, and ¼ inch brass or ½ inch alu tubes.
  • 24g/370gr – size 6-4 single hooks, size 10-6 double hooks, ½ inch brass and ¾ inch alu or 1-inch plastic tubes.
  • 26g/401gr – size 6-4 single hooks, size 10-4 double hooks, ½ inch brass and ¾ inch alu or 1-inch plastic tubes.
  • 28g/432gr – size 10-4 double hooks, ¾ inch brass, and 1-inch alu and 1-½ inch plastic tubes.
  • 31g/478gr – size 1-inch brass, 1-¼ alu tube and 1-½ inch plastic tubes.
  • 33g/509gr – 1-inch brass, 1-¼ alu and 1-½ inch plastic tubes.
  • 35g/540gr – 1-¼ inch brass, 1-½ alu and 2-inch plastic tubes.