Fish Weight Formula

Many folks are fishing catch and release waters - or just prefer to release their fish for another time. That said, it would be kind of nice to have a good estimate on what that fish weighs. This formula is mostly used on large steelhead, and if you have one for other fish, please let us know and we will include it.

Girth dimension plays a large role in more accurately calculating weights of released fish, the "Length Minus 20 Rule" is the simplest method of determining a steelhead's weight. To get the approximate weight of a 29-inch steelhead subtract 20 inches and you come up with 9 pounds. Simple; and this works for average-girthed steelhead, plus or minus 10%, in the 25 to 35-inch range. To be accurate, measure the fish from it's nose to the fork of the tail. This method will give you a quick estimate of weight before releasing the fish.

However, if your fish looks deep and/or is greater than 35 inches long, you may want to determine a more accurate weight. Use Sturdy's Formula below.

Study's Formula Weight Chart

For example, a large 43-inch fish with a 21-inch girth would be calculated by following along the top, marked LENGTH, until you find 43 then go down the side, marked GIRTH, until you find 21. The weight is 25.2 pounds.

You might want to print the chart out for future use! Good fishing!

CREDITS: The information and chart of Sturdy's Formula are from The Dean River part of the Steelhead River Journal series Published by Frank Amato Publications.

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