Fishing calculators built on published equations
Seven tools, every one of them running an equation you can trace to the agency or paper that published it. No account, no email, no app. If a number here cannot be sourced, it does not ship — the build fails instead.
Most were built for the Upper Mississippi, which is where we fish. The weight and line calculators work anywhere; thelicense finder is specific to the Wisconsin, Minnesota and Iowa boundary waters covered in ourMississippi River guide.
Fish weight calculator
What does a fish of this length weigh?
Covers channel catfish, walleye and largemouth bass in one tool, using a separate published equation for each. Start here if you are not sure which species you caught.
Catfish weight calculator
What does this channel catfish weigh?
Channel catfish only, with the flathead and blue catfish differences spelled out and the fork-length trap explained. Valid down to 70 mm total length.
Walleye weight calculator
What does this walleye weigh, and is it actually a sauger?
Walleye only, with a two-second sauger identification check up front and the spring egg-weight swing worked through in numbers.
Largemouth bass weight calculator
How long is a five-pound bass?
Largemouth only. Answers the five-pound question as a two-inch window rather than a single length, and shows why bass outrun a cube-law guess.
Fishing line capacity calculator
How much braid fits a spool rated for monofilament?
Swap any two lines from the Berkley, Seaguar and PowerPro spec tables and see the yardage, with a tolerance band because published diameters are rounded.
Best fishing time calculator
Is this a good hour to be on the water?
Four factors scored separately, each labeled with how strong the evidence behind it is. No percentage, because no validated model exists to produce one.
Mississippi River fishing license finder
Which state license do I need on the boundary water?
Wisconsin, Minnesota and Iowa prices with the reciprocity rules applied properly, including the resident rule almost everyone gets backwards.
What is each calculator actually built from?
| Calculator | Question it answers | Built from |
|---|---|---|
| Fish weight calculator | What does a fish of this length weigh? | Standard-weight equations from published fisheries research |
| Catfish weight calculator | What does this channel catfish weigh? | Brown, Murphy and Springer (1995), 241 populations |
| Walleye weight calculator | What does this walleye weigh, and is it actually a sauger? | Murphy, Brown and Springer (1990), 42,487 fish |
| Largemouth bass weight calculator | How long is a five-pound bass? | Henson (1991) standard-weight equation |
| Fishing line capacity calculator | How much braid fits a spool rated for monofilament? | Manufacturer diameter tables and spool geometry |
| Best fishing time calculator | Is this a good hour to be on the water? | NOAA solar equations plus our own published weights |
| Mississippi River fishing license finder | Which state license do I need on the boundary water? | State administrative code and agency price pages |
Why does everything here come with a range?
Because precision you have not earned is a lie with decimal places. A standard-weight equation describes a population of fish, not the one in your hands. A published line diameter of 0.011 inch is a rounded figure that could be anywhere from 0.0105 to 0.0115, and diameter is squared in the capacity calculation. A fishing-conditions score has no validated model behind it at all.
Every one of those facts is knowable, and every competing tool we looked at hides all three behind a single confident number. Showing the range is not hedging. It is the result.
Where does advertising sit on these pages?
Below the calculator, never beside it, and never within a screen of the result panel. The most common complaint we found while researching competing fishing tools was ad units covering the calculate button. Our tools have no calculate button — they recalculate as you type — so there is nothing to cover, and the ad-free zone below the result is enforced in the page layout rather than left to judgement.
Questions about these tools
Are these calculators free?
Yes, all seven, with no account and no email required. The site carries advertising, and no ad is placed within a screen of any calculator result panel.
Why do the results show ranges instead of single numbers?
Because the inputs do not support single numbers. A published fish-weight equation describes a population, and a published line diameter is rounded to three decimal places. A range is what the underlying data actually supports.
Do these work on a phone with no signal?
Once a page has loaded, yes. All the maths runs in your browser and none of it calls a server, so a calculator you opened at the boat ramp keeps working out on the water.
How often are the numbers rechecked?
Every source has a verification date, and the build refuses to publish if any source is more than 180 days past its last check. That is enforced by a script, not by a reminder in someone's calendar.
What should you open next?
If you came here after catching something, start with thefish weight calculator. Respooling before a trip is thefishing line capacity calculator; picking a dawn or dusk window is thebest fishing time calculator. If you are planning a trip to the river rather than reporting one, thePool 8 guide is the better first stop, and the license finder settles the paperwork before you drive.