Jack Russells range in height from 10 to 15 inches at the shoulder and weigh 13 to 17 pounds, but you can find them in a wide range of sizes. Some adult Jack Russells may weigh as little as 10 pounds, while others may weigh more.
The breed’s height also varies, with some dogs standing as tall as 15 inches at the shoulder and others standing only 12 inches tall. The AKC standard calls for a smaller range of 12 to 14 inches.