How long is a full grown snail?

Snails come in a wide range of sizes. The smallest snail species, Acmella nana, is only about 0.02 inches (0.5 millimeters) long when fully grown. The largest snail species, the African land snail (Achatina fulica), can grow up to 8 inches (20 centimeters) long. Most snail species are between 0.2 and 1.0 inches (5 and 25 millimeters) long when fully grown.