Average 6-7 inches, can grow to 10 inches
One of the most popular items on Washington seafood menus is the Dungeness crab. This hardshelled crustacean is fished from the Aleutian Islands to Mexico. The shell is purple-tinged, gray or brown on the back and the tips of the claws are typically white. The Dungeness crab can reach ten inches across the back though six to seven inches is more common. In Puget Sound this crab is most abundant north of Seattle, in Hood Canal, and near the Pacific coast. The Dungeness crab is frequently associated with eelgrass beds and prefers sandy or muddy substrates.
For rules, seasons and more identifcation on Dungeness crab see: http://wdfw.wa.gov/fishing/shellfish/crab/