Corn snakes are popular as pets because they do not grow as large as boas and pythons and they are relatively easy to care for. Unlike boas and pythons, which can grow in excess of 1.8 m (6 feet), corn snakes stay slender and only grow to an average size between 90 cm and 1.5 m (3 feet and 5 feet). Because most corn snakes follow the same growth pattern, it is possible to estimate a corn snake's age using its length if you have a growth chart to reference.
Lay your corn snake out on a flat surface and stretch him to his full length. It helps if you have a second person to assist you in keeping your snake's head and tail stationary while you measure.
Measure the length of your corn snake from the tip of his nose to the tip of his tail using a measuring tape. Record this measurement on a piece of paper and put your snake back in its cage.
Narrow down your snake's age using the following guidelines: At birth, most corn snakes measure less than 25 cm (10 inches) in length, and by one month they can be as long as 37.5 cm (15 inches). At six months corn snakes can measure around 50 cm (20 inches), but after six months they tend to grow more slowly. If your corn snake measures 50 cm (20 inches) or less, you can assume it is younger than six months of age.
Estimate your corn snake's age more accurately by comparing its length to the following guidelines: At one year, corn snakes average a length of between 62.5 and 70 cm (25 inches and 28 inches). At two years, they can be as long as 1.07 m (43 inches). At age three, corn snakes can measure as long as 1.2 m (4 feet).
Corn snakes live an average of 15 to 20 years in captivity, and they grow to an average size between 60 cm and 1.8 m (24 inches and 72 inches). If your snake measures in at the higher end of this spectrum, you can assume that it is in its adulthood, possibly as old as 10 or 15 years.
Keep in mind that, like humans, not all corn snakes grow at the same rate. Baby corn snakes tend to grow much more quickly in their first few months, which makes accurate age estimation difficult. Different breeds and hybrids of corn snakes may also grow differently, and the type of food and the frequency with which a corn snake eats also affects its rate of growth.