What Is the Average Size of a Tuna Fish?

The average size of a tuna fish ranges between around 15 inches to about 79 inches. The average weight varies greatly, from as small as 3 pounds to as large as 400 pounds.

The average size of a tuna fish depends upon the species of the tuna fish. An albacore tuna fish averages around 15 to 40 inches in length and has a weight of approximately 10 to 25 pounds. The Atlantic or northern bluefin tuna, one of the largest species, weighs around 550 pounds.