This salmon calculator is a quick and easy solution to use for determining the weight of a fish that has been measured and released. 
Using the calculator is very easy. Simply enter the measurements into the appropriate boxes. 

Length is measured from the tip of the nose to the center of the tail. 
Girth is measured just in front of the dorsal fin.

Remember to use a soft tape and keep in mind that when your fish is out of the water it is experiencing the same thing you do when you are under water, so if possible measure the fish in the water.