The dimensions of bed mattresses are 39-by-75 inches for twin-sized mattresses, 54-by-75 inches for full-sized mattress, 60-by-80 inches for queen-sized mattresses and 76-by-80 inches for king-sized mattresses. The California king-sized mattress is 72 inches wide and 84 inches long, which is well-suited for tall adults.
The extra-long twin-sized mattress is 39-by-80 inches and is commonly used for beds in college dorms. While mattress dimensions are standardized, the thickness of a mattress can vary by model and brand, depending on different levels of physical support and quality. The thickness of crib mattresses is regulated by law and can be no more than 6 inches thick. The dimensions for crib mattresses are 27-by-52 inches to fit snugly into cribs, leaving a gap-width of no more than two fingers for the child's safety.
Full-sized mattresses are designed to provide enough sleeping space for a single person under 5 feet 5 inches tall and are used as a step-up mattress for teenagers. Queen-sized mattresses are 6 inches wider than full-sized mattresses, and provide each adult with approximately 30 inches of sleeping space, which is less than a single twin-sized mattress.
The king-sized mattress provides two adults with as much sleeping space as two extra-long twin-sized mattresses pushed together. King-sized mattresses are generally paired with two half-width box springs to make navigating hallways, stairwells and doorways more manageable during moves.