If you have the length and width of a steelhead and want to know how much it weighs, take the length times the width squared, and divide that number by 775. For expample, if you catch a steelhead that's 39" x 20", enter in the calculator: 39 x 20 x 20, and divide that number by 775. It will give you the weight within a couple of ounces. Truthfully, I was a little skeptical at first on how well it would work. So when I caught a hatchery fish, I'd take the dimensions, and enter the formula in the calculator. Then I'd take the same fish and weigh it on a digital scale. I did this a number of times, and every time the formula was right on. It also works on silvers, chinook, chums, etc.. Remember though, to measure the length from the snout to the middle of the tail, and measure the girth just in front of the dorsal fin.