Of the average shrimp size that is commonly eaten, 3 ounces of shrimp is usually four or five pieces of shrimp. This shrimp, labeled 21/25, averages 23 shrimp per pound.
There is one other common labeling of shrimp, the 41/50 label. On average, shrimp labeled this way comes 45 shrimp to the pound. There are 16 ounces in a pound. Three-sixteenths of this number is approximately 8.4, so there are about eight or nine shrimp in 3 ounces. The larger the shrimp, the smaller the number assigned to it because it takes fewer large shrimp to make a pound. There are other sizes of shrimp, but these two are the most common.