Got my personal best Flathead today, a 39-40 incher with fat little bellies on each side. What does an average 40 incher weigh? Got a 33-34 incher on Friday, I was guessing 20-25 pounds. The smaller one didn't have the prominent fat sides that the big one had.

Tough to estimate without a picture.Flatheads are deceiving in any case because they "Look" bigger than they are ,at least to me.There is a weight formula based on length and girth but I can't re call it.:smile2:

There is a formula: length x girth x girth / 800=weight that works pretty good. I've found it to be pretty close to scale weights, but it will vary some. Flatheads are long and lanky compared to blues, and can look larger than they are, as Jim stated.

Not knowing the girth of your fish makes it difficult to say. My son caught one that was 40" and it weighed 28 lbs. You can see that flattie in member fishing reports/ Hocking River 08/19.