how to calculate the weight of a fish

Fish Weight Calculator

Have you ever wondered how much that trophy fish you caught actually weighed? We can all remember exactly how long our fish were by the distance between our hands as we tell the story of the one that got away, but how heavy was it? We’ve put together a fish weight calculator for you to input your last catch into our weight calculator algorithm.

We have put together two apps for you to use, the first calculates an estimated girth of the fish based on they type of fish. Our second average weigh calculator will help you determine exactly how much that fish would have weighed! Let’s get going. If you need more help with fly fishing basics before getting started head back to our homepage.

How to Measure a Fish

Measure a fish’s length

Take the measuring tape and lay it beside the fish. Take a measurement from the very top of the nose of the fish to the end of the tail. To make sure you get an accurate reading on the length of the tail make sure the tail is pinched together. It is this measurement that will be multiplied by the girth x girth measurement in the calculator below. 

how to measure a fish's length
Image source: Wikihow

How to Measure Girth of a Fish

Find the widest part of the fish as close to the dorsal fin as possible, without including it. You can use a flexible tape measure (if you have one) or a piece of string. Wrap it around the fish and take the measurement (in inches). Note this measurement as the girth of the fish.

how to measure a fish's girth
Image source: Wikihow

The Calculators

So to continue with the estimation of the weight of the fish we’re going to at least need to know the length of the fish. Most people can at least remember by extending their arms as wide as they can, then measure the distance between your fingertips. That tends to be about how long most fish are, so let’s calculate how heavy our fish was.

Final words

NOTE: This is a tool for estimating your fish weight. Just like people, fish come in a number of different shapes and sizes. Use this fish to estimate the weight of your fish so you can turn “this big” into actual numbers. If you like the tool feel free to share it with your friends by using the sharing options.

The following journals were used during the formulation of this calculator: