Northern Pike Weight
The formula to calculate the weight for a Northern Pike that is 40 inches long and has a girth of 20 inches is as follows. Northern Pike have a shape factor of 1000 and a girth ratio of (.52)
WEIGHT = LENGTH x GIRTH2 / SHAPE FACTOR
WEIGHT= 40 x (202) / 1000
WEIGHT= 40 x 400 / 1000
WEIGHT= 16000 / 1000
WEIGHT = 16.0 pounds
Please Note: A 40 inch pike might be thicker than normal and have a girth of 22 inches, which would make the fish 19.4 pounds.