Frequently Asked Questions
How do I estimate a fish weight from measurements?
With girth, multiply length by girth squared and divide by 800. With length only, cube the length and divide by a species shape factor such as 1600 for bass.
Where do I measure a fish girth?
Measure girth at the fattest part of the body, just ahead of the dorsal fin, wrapping the tape snugly around the fish. Use total length from snout to tail tip.
Why does the formula change by species?
Different species have different body shapes and densities. Pike are long and slender (factor 3500) while catfish are stout (factor 1200), so each uses a tailored shape factor.
How accurate are these weight estimates?
Length-and-girth estimates are quite close for healthy fish, but they remain approximations. A spawning fish or one full of forage can weigh noticeably more than predicted.
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Fishing & Hunting Disclaimer: Estimates only. Verify regulations and practice safety.
This calculator is for educational and informational purposes only. Bag limits, seasons, legal methods, and equipment rules vary by state and locality and change frequently, so always confirm current regulations with your state wildlife agency before fishing or hunting. Follow all firearm and tree-stand safety practices.