Blue cats are the heavyweight champions of North American rivers, growing past 100 pounds. This blue catfish length-to-weight chart estimates weight from length using state fisheries data, so you can size up a big blue before the release.
Blue catfish length-to-weight chart
| Length | Average weight |
|---|---|
| 16″ | 1.29 lb |
| 18″ | 1.91 lb |
| 20″ | 2.72 lb |
| 22″ | 3.75 lb |
| 24″ | 5.02 lb |
| 26″ | 6.56 lb |
| 28″ | 8.41 lb |
| 30″ | 10.6 lb |
| 32″ | 13.2 lb |
| 34″ | 16.1 lb |
| 36″ | 19.5 lb |
| 40″ | 27.8 lb |
| 44″ | 38.3 lb |
These figures are calibrated to Missouri Department of Conservation data from over 2,000 measured blue catfish. Blues get relatively heavier per inch as they grow, so the very biggest fish can top the chart.
What’s an average blue cat — and what’s a trophy?
A common “eater” blue catfish runs 24–30 inches and 5–11 pounds; fish over 30 pounds show up regularly in productive systems but aren’t the average catch. Anglers treat 30 pounds as the informal trophy line, 50 lb+ as a genuine trophy, and 100 pounds as the fish of a lifetime (conventions, not official marks). The IGFA all-tackle world record is a massive 143 pounds, caught at Kerr Lake, Virginia, in 2011 — 57 inches long with a 44-inch girth.
Put a number on your exact fish (worked example)
Blue catfish are broad, heavy-bodied fish, so girth adds up fast:
Weight (lb) = Length × Girth² ÷ 800
A 40-inch blue with a 30-inch girth works out to 40 × 30 × 30 ÷ 800 = 45 lb, well above the ~28 lb length-only average — a true tank. Measure both and use our free fish weight calculator; see how to estimate a fish’s weight.
Why two blue cats of the same length weigh differently
Reservoir blues gorging on shad grow much heavier than river fish fighting current at the same length. Pre-spawn females are heaviest in late spring, and because blues bulk up so much as they age, the divisor that fits a small fish underestimates a giant — which is why girth wins for big cats.
Where and when to find bigger blue catfish
Blue cats hold in deep channels and holes of big rivers and reservoirs, along main-channel edges and current seams. They tolerate turbid and even brackish water, which is why they’ve become abundant (and invasive) in Chesapeake Bay tributaries. The standard trophy approach is fresh cut shad or herring fished on the bottom with circle hooks in current. ID: a straight-edged (flat) anal fin with 30–36 rays and a uniform slate-blue body, versus the channel catfish’s rounded anal fin and dark spots.
Blue catfish weight FAQ
How much does a 40-inch blue catfish weigh? About 28 pounds on average, and considerably more if it’s a thick, well-fed fish.
What’s a trophy blue catfish? Around 30 lb informally; 50 lb+ is a genuine trophy.
How do I tell a blue from a channel catfish? Blues have a straight-edged anal fin and no spots; channels have a rounded anal fin and dark spots.
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