How to Estimate a Fish's Weight Weigh a fish without a scale | The Old Farmer's Almanac

How to Estimate the Weight of a Fish

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Fishing the Salmon River, Polaski, NY

Photo Credit
Mary Jaeger
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Here’s how to estimate the weight of a fish.

  • Measure the fish from the tip of its nose to the tip of its tail.
  • Then measure its girth at the thickest portion of its midsection.

Weight of a fat-bodied fish
(bass, salmon)
(length x girth x girth)/800

Weight of a slender fish
(trout, northern pike)
(length x girth x girth)/900

If a fish is 20 inches long and has a 12–inch girth, its estimated weight is
(20 x 12 x 12)/900
2,880/900=3.2 pounds

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