🐟 Fish Weight Estimator
Quickly estimate the weight of your catch using standard length-weight formulas for common species.
Northern strain; length in inches, weight in pounds.
Measure from snout to fork tip.
Estimated Weight (Length Formula)
6.94 lb
3.15 kg
How to Use This Calculator
Select fish species
Different species have unique length-to-weight relationships.
Measure length
Use a bump board or tape measure for accurate length.
Optional girth measurement
Wrap a soft tape around the widest body section.
Review estimated weight
Compare length-only and girth-adjusted results for accuracy.
Formula
Weight = a × Lengthᵇ (species-specific constants a and b)
Girth formula: Weight = (Length × Girth²) ÷ 800
Length in inches, weight in pounds. Convert to metric by multiplying pounds × 0.453592.
Length-weight coefficients come from fisheries data; adjust for local populations if you have your own catch records.
Catch & Release Tips
Quick measurements help release fish safely. Keep fish in the water while measuring girth, and use wet hands to protect the slime coat.
Best Practices
- Use barbless hooks and handle fish minimally.
- Support heavy fish horizontally to avoid organ damage.
- Carry a flexible measuring tape and bump board for quick readings.
Frequently Asked Questions
How accurate are these estimates?
They’re based on population averages. For trophy or region-specific fish, calibrate with local catch data.
Can I use centimeters?
Yes—convert length to inches (cm ÷ 2.54) before input. Final weight can be converted to kilograms.
Why include girth?
Girth accounts for body condition—useful for pre-spawn, post-spawn, or unusually thick fish.
Does water temperature affect weight?
Weight vs length doesn’t depend on temperature, but fish condition varies seasonally. Adjust expectations accordingly.
What if my species isn’t listed?
Use the closest match or research local length-weight coefficients from fisheries agencies.