About These Formulas
These formulas have been developed through extensive empirical data and research. While they typically provide good results, please note that they are estimates and actual weights may vary depending on various factors including the fish's condition and season.
Formula Types
Length × Girth² Formula
Weight = (Length × Girth × Girth) ÷ Factor
Freshwater Species
Largemouth Bass
÷ 800
Rainbow Trout
÷ 750
Brown Trout
÷ 730
Lake Trout
÷ 800
Brook Trout
÷ 800
Walleye
÷ 750
Northern Pike
÷ 900
Channel Catfish
÷ 850
Flathead Catfish
÷ 850
Blue Catfish
÷ 800
Chinook Salmon
÷ 740
Bluegill
÷ 1,200
Saltwater Species
Redfish
÷ 900
Bluefish
÷ 900
Red Snapper
÷ 800
Spanish Mackerel
÷ 900
Common Snook
÷ 900
Bonefish
÷ 900
Cobia
÷ 800
Yellowfin Tuna
÷ 800
Greater Amberjack
÷ 800
Halibut
÷ 625
Croaker
÷ 900
Length³ Formula
Weight = (Length × Length × Length) ÷ Factor
Freshwater Species
Crappie
÷ 1,600
Yellow Perch
÷ 2,200
Saltwater Species
Flounder
÷ 2,500
Sheepshead
÷ 1,200
Florida Pompano
÷ 2,500
Seatrout
÷ 2,200
Special Formula
Tarpon
((Length × Girth²) ÷ 800) × 1.13
Tarpon uses the standard Length × Girth² formula with an additional 1.13 multiplier for accuracy.
App Features
Free Species (12)
6 freshwater and 6 saltwater species available with basic app download
Pro Species (18)
Additional premium species available with subscription upgrade
Measurement Guidelines
- 1. Length: Measure total length from tip of snout to tip of tail (not fork length)
- 2. Girth: Measure circumference at the widest/thickest part of the fish
- 3. Units: All measurements can be input in inches or centimeters - the app handles conversion
- 4. Accuracy: More precise measurements yield more accurate weight estimates
- 5. Condition: Fish weight varies by season, feeding, and spawning condition