Estimate fish weight from length and girth without a scale. This fish weight calculator works for bass, trout, catfish, walleye, pike, muskie, salmon, carp, panfish, and general catches using common length-girth formulas and species adjustment factors.
Length and girth:
The calculator uses fish length and girth to estimate weight. Girth is especially important because a thicker fish can weigh much more than a fish of the same length.
Species:
Different fish have different body shapes. A deep-bodied carp or catfish may weigh more than a slender pike with similar length.
Condition:
The body condition setting adjusts for thin, average, healthy, or trophy-build fish.
A fish weight calculator is useful when you want a quick catch estimate without carrying a scale, especially for catch-and-release fishing.
Actual fish weight depends on species, body shape, season, spawn timing, stomach contents, girth measurement, length measurement, and scale accuracy.
This calculator uses a common length-and-girth estimate:
Fish Weight = Length × Girth² ÷ Divisor
Measure the fish length and girth, then use a length-girth formula. This gives a practical estimate, but it is not as accurate as a scale.
Measure around the thickest part of the fish, usually near the belly or just ahead of the dorsal fin depending on the species.
Fish weight rises quickly with body thickness. In the common formula, girth is squared, so small girth changes can make a large weight difference.
No. This is an estimate for planning and fun. Official fish records usually require a certified scale and specific measuring rules.