Cars & Other Vehicles What is king size bed? What is king size bed? King-size mattresses are 80 inches long and 76 inches wide. A king bed gives you plenty of room to sleep with a partner. In comparison to a queen mattress, a king bed has 8 inches more width per person.Nov 17, 2021 Related Posts:Marriott Official Bed is Medium to Firm Support and is available on Amazon.com.There is a guide to standard sofa sizes and dimensions.Can full sheets fit a queen?What mattress is bigger than a queen?