Fish Weight Estimator (Length & Girth)
No scale on the boat? Estimate a fish's weight using just a tape measure. Enter the length and girth (and species type) to get a quick weight estimate using the standard angler formula.
About this calculator
Estimate a fish's weight from its length and girth measurements using standard length-girth weight formulas, useful for catch-and-release anglers who want a quick estimate without a scale.
Frequently Asked Questions
How accurate is the length-girth weight formula?
It's an estimate, typically within 10-15% of actual weight. It works best on fish with typical body proportions for their species.
Where do I measure girth?
Measure around the fish's widest point, usually just behind the pectoral fins/gill plates, using a soft measuring tape.
Why does species/body shape matter?
Slender fish like pike carry less weight per unit of girth than round-bodied fish like catfish, so the formula divisor is adjusted to reduce systematic error.