How heavy is a 16-inch bass? What does a 12-inch crappie weigh? Length tells you more about a fish than anything else you can measure in a boat, and this chart converts it into pounds for the species North American anglers catch most.
These figures come from standard length-to-weight conversions used by state fisheries agencies. They describe a fish in average condition — a fish with a full belly or a female full of eggs will weigh more, sometimes considerably more.
| Length | Largemouth | Smallmouth | What it is |
|---|---|---|---|
| 10 in | 0.5 lb | 0.5 lb | Young fish, well under any keeper size |
| 12 in | 0.9 lb | 0.9 lb | Common catch on most lakes; a good panfish-scale bass |
| 14 in | 1.5 lb | 1.4 lb | A legitimate keeper in most states |
| 16 in | 2.3 lb | 2.1 lb | A solid fish anywhere in North America |
| 18 in | 3.2 lb | 3.0 lb | The classic “good one” — worth a photo |
| 20 in | 4.3 lb | 4.0 lb | A big fish on most water, a tournament fish on many |
| 22 in | 5.6 lb | 5.4 lb | Trophy class in the north, a good fish in the south |
| 24 in | 7.2 lb | 7.1 lb | A genuine trophy in most fisheries |
| Length | Walleye | Northern pike | Channel catfish |
|---|---|---|---|
| 12 in | 0.6 lb | — | 0.8 lb |
| 15 in | 1.1 lb | — | 1.6 lb |
| 18 in | 1.9 lb | — | 2.8 lb |
| 21 in | 2.9 lb | — | 4.5 lb |
| 24 in | 4.3 lb | 3.0 lb | 6.8 lb |
| 28 in | 7.1 lb | 4.8 lb | 10.9 lb |
| 32 in | 10.5 lb | 7.2 lb | 16.1 lb |
| 36 in | — | 10.3 lb | 22.8 lb |
| 40 in | — | 14.5 lb | — |
| 44 in | — | 19.5 lb | — |
Pike and catfish both have long, slender body shapes at the front and heavy shoulders at the back, so length is a looser guide for them than it is for bass or walleye. A pike measured from the tail fork rather than the tail tip reads several inches short.
| Length | Bluegill | Crappie | Yellow perch | Rainbow trout |
|---|---|---|---|---|
| 6 in | 0.3 lb | 0.1 lb | 0.1 lb | 0.1 lb |
| 8 in | 0.7 lb | 0.3 lb | 0.3 lb | 0.2 lb |
| 10 in | 1.3 lb | 0.6 lb | 0.6 lb | 0.4 lb |
| 12 in | — | 1.0 lb | 1.1 lb | 0.7 lb |
| 14 in | — | 1.7 lb | 1.7 lb | 1.1 lb |
| 16 in | — | 2.6 lb | 2.5 lb | 1.7 lb |
| 18 in | — | — | — | 2.4 lb |
| 20 in | — | — | — | 3.2 lb |
| 24 in | — | — | — | 5.4 lb |
A 9 to 10 inch bluegill is a large one in most waters. State record bluegills run 4 to 5 lb and are extremely rare — a one-pound bluegill is already a notable fish.
| Species | Solid keeper | Trophy | Note |
|---|---|---|---|
| Largemouth bass | 2–3 lb | 8 lb+ north, 10 lb+ south | A 10 lb bass is roughly 26 inches long and very thick through the body |
| Smallmouth bass | 2–3 lb | 6 lb+ | A 6 lb smallmouth is a once-a-season fish almost anywhere |
| Walleye | 2–4 lb | 10 lb+ | A 30 inch walleye is the usual trophy marker |
| Northern pike | 3–6 lb | 20 lb+ | Northern fish grow slower than southern ones; a 44 inch pike is exceptional |
| Crappie | 0.75–1 lb | 2.5 lb+ | A 14 inch crappie is a big one; anything over 2 lb is a serious fish |
| Channel catfish | 2–5 lb | 20 lb+ | Blues and flatheads grow much larger than channels |
To estimate a fish in the boat, measure length and girth and run it through the Fish Weight Calculator, which uses the classic length × girth² formula. Then check the fillet yield calculator to see what it will actually feed.
Length and girth take ten seconds and turn an estimate into a number you can repeat.
The only way to know. Buy 50 lb rather than 15 lb so one scale covers panfish and the fish of a lifetime.
Check current price on Amazon →A bump board gives you a repeatable length, which is what turns a weight estimate into something you can compare year to year.
Check current price on Amazon →For girth, measured around the deepest part of the body. Girth is squared in the formula, so accuracy here matters most.
Check current price on Amazon →TackleCalc takes part in the Amazon Associates Program: qualifying purchases through our links may earn us a commission. Prices and availability are set by Amazon and change without notice. Read our full affiliate disclosure.
Typical size ranges are the quickest way to judge a catch. The fish weight calculator estimates weight from length, the seasons by species chart shows when each is catchable, and the fillet yield calculator turns the size into meat.
About 3.2 lb for a largemouth in average condition. Length alone gives you a rough answer, and it swings widely: a fat pre-spawn female at 18 inches can touch 4 lb, while a spawned-out fish the same length may weigh under 2.5 lb. Girth is what separates them.
Measure length from the snout to the tail and girth around the deepest part of the body, then use length × girth² ÷ 800. If you cannot measure girth, use the table on this page for the species — but understand the estimate carries a 15 to 20% error band, which is the difference between a 3 lb and a 4 lb fish.
For bluegill, 7 to 8 inches is the usual eating size — about 0.5 to 0.7 lb. For crappie, 10 to 12 inches, which is roughly 0.6 to 1 lb. Many states set minimum lengths, so check your local regulations before keeping anything.
It depends on the species and the water, but a useful rule is a fish in the top few percent of its local population. For largemouth bass that is 8 lb or more in most northern waters, 10 lb in the south. For walleye, 10 lb. For pike, 20 lb. Those are the numbers worth mounting or photographing carefully.
Three reasons: condition, sex and season. A female carrying eggs in spring can weigh 15 to 20% more than a spawned-out male of the same length. A fish from a lake full of bait is measurably heavier than one from a lake with little food. Length is a skeleton; weight is condition.
Fish Weight Calculator · Fillet Yield Calculator · How to weigh a fish without killing it · Fishing line strength chart · Hook Size Selector
Fish Weight Calculator · Fillet Yield Calculator
Charts on the same subject: Fishing Seasons by Species · Fish Water Temperature Chart
Estimates only: the values shown are a starting point, not a guarantee. Products of the same stated size differ between makers, so your own result will vary. TackleCalc is not affiliated with any manufacturer, and these figures are a guide rather than a guarantee.