The weight of a newborn pig varies depending on the species and health of the piglet. A healthy commercial pig weighs as much as 3 to 4 pounds at birth. A smaller pig weighs as little as 1 to 2 pounds at birth.
There are over 70 breeds of pig in the world, and their weights vary widely. A miniature pig weighs about 9 ounces at birth, and only grows to about 50 pounds even as an adult. A newborn commercial pig grows quite quickly, and a healthy pig of this type weighs up to 50 pounds by the time it reaches four weeks old. Commercial pigs reach weights in excess of 300 pounds as adults.