Fish Size to Weight Calculator [Bass, Pike, Trout]

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Written By Russ Egan

Russ is a professional fisherman with over 20 years of experience. He has fished all over the world for more than two decades, primarily for saltwater game fish but also for local trophy fish. Russ comprehensively tests and reviews all his fishing gear to help others achieve their own fishing goals. There is nothing he prefers than heading down to his local tackle store, buying the latest fishing reel, and taking it to the water to test.


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This Fish Weight Calculator is an essential tool for anglers seeking quick estimates of their catch’s weight. Ideal for fishing enthusiasts of all levels, it calculates fish weight based on length, girth, and species, helping anglers record their achievements and compare catches accurately.

This tool was developed for Largemouth Bass, Smallmouth Bass, Trout, Salmon, Walleye, Bluegill, Salmon, Northern Pike, and Crappie.

Fish Weight Calculator

How to Use the Fish Weight Calculator

If you’re an angler and you want to estimate the weight of a fish you’ve caught based on its length, girth, and species, this Fish Weight Calculator can be a handy tool. This guide will walk you through how to use the calculator effectively.

Step 1: Gather the Necessary Measurements

Before you can use the Fish Weight Calculator, you need to have some information ready:

  1. Fish Length (in inches): Measure the total length of the fish from the tip of its nose to the end of its tail. Be as accurate as possible, and enter this value into the “Fish Length” field.
  2. Girth: Estimate the fish’s girth, which is the measurement around the fish’s body, typically at its widest point. You have three options to choose from in the “Girth” dropdown:
    • Skinny: Choose this option if the fish appears thin or slender.
    • Average: Select this if the fish has an average girth.
    • Fat: Use this if the fish looks particularly plump or thick.
  3. Fish Type: Identify the species of the fish you’ve caught. Use the “Fish Type” dropdown to select the appropriate fish species from the list provided. Different species have different weight factors, so this choice is crucial for an accurate estimate.
Fish Size to Weight Calculator [Bass, Pike, Trout] 1

Step 2: Input the Information

Now that you have all the necessary information, input it into the calculator:

  • Enter the fish’s length in inches into the “Fish Length” input field.
  • Choose the appropriate girth level from the “Girth” dropdown.
  • Select the fish species from the “Fish Type” dropdown.

Step 3: Calculate the Estimated Weight

Once you’ve entered all the required information, click the “Calculate” button. The calculator will use a predetermined formula based on the fish species and girth to estimate the fish’s weight.

Step 4: Review the Estimated Weight

After clicking the “Calculate” button, the estimated weight of the fish will be displayed in the “Estimated Weight” section below the calculator. This weight will be in pounds (lbs).

Step 5: Record and Share

Now that you have an estimated weight for your fish, you can record this information in your fishing log or share it with fellow anglers. Knowing the approximate weight of your catch can be helpful for bragging rights, competition, or simply for keeping track of your fishing successes.

How It Works

The Fish Weight Calculator uses a formula that takes into account the length, girth, and species of the fish to estimate its weight. Different fish species have different weight factors, and the girth level helps adjust the estimation based on the fish’s body shape.

The formula used for the estimation is:

Weight (lbs) = (Fish Length * Fish Length) * Weight Factor

  • Fish Length: The length of the fish in inches.
  • Weight Factor: A factor specific to the chosen fish species and girth level.

The calculator uses these factors to provide you with a reasonably accurate estimate of the fish’s weight.

Keep in mind that this calculator provides approximate values and may not be 100% accurate, as fish weights can vary based on several factors. However, it can be a useful tool for anglers looking for quick estimates while out on the water.

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