If you only measured length, CatchLogBook uses a body-shape formula instead: chunky fish like bass are heavier for their length than trout or walleye, and slender fish like pike are lighter. Log the estimate with the catch so your personal bests stay comparable.
How the stats work
Every catch you log feeds the stats panel. Baits, spots and times of day are counted case-insensitively, so “Jig” and “jig” are the same bait, and the top three of each are shown with their counts. Time of day is grouped into early morning, late morning, afternoon, evening and night. Personal bests keep the heaviest fish of each species, using length to break ties, and a trip is any unique combination of date and spot. Release rate is simply the share of logged fish marked as released.
The numbers become useful surprisingly quickly. After a dozen outings most anglers find that one or two baits account for most of their fish and that their best spot is not the one they visit most. Keep notes on depth, retrieve, wind and tide in the notes field and you will know how to repeat a good day.
Estimating weight without a scale
The girth formula, length × girth² ÷ 800 in inches and pounds, has been used by anglers and guides for decades and works for most fish shapes. When you only have a length, CatchLogBook uses a cube-of-length rule with a divisor set by body shape: about 1,600 for chunky fish such as bass and panfish, 2,700 for trout, walleye and salmon, and 3,500 for long, slender pike and muskie. In metric the calculator converts centimetres to inches, applies the formula and converts the result back to kilograms.
Your spots stay yours
CatchLogBook has no accounts and no server-side storage. Catches are saved in local storage in this browser, so nobody else can see where you fish. Use Download backup to keep a copy or move the log to another device, and Export CSV to open it in a spreadsheet.
Frequently asked questions
How do I measure girth?
Wrap a soft tape around the fish at its widest point, usually just in front of the dorsal fin. Do it quickly and keep the fish wet.
How much does a 20 inch walleye weigh?
About 3 lb from length alone. With a 12 inch girth the girth formula gives 3.6 lb.
How accurate are these formulas?
Usually within about 10–15%. Spawning or very lean fish will be further off; a certified scale is the only exact answer.
Is CatchLogBook free?
Yes. The fishing log, weight calculator and printable sheets are free with no account.
Where is my log stored?
Only in this browser on this device. Download a backup now and then so you never lose a season.