A crib mattress, also known as a "baby mattress" or "toddler mattress," is commonly the first mattress a child will sleep on. The standard size of a crib mattress can vary but most importantly, the crib mattress that you purchase must fit the dimension of the crib exactly so that there are no spaces left in the crib to present a safety hazard for the child.
Twin mattresses come in standard and XL sizes. Traditional twin mattress dimensions are 38-by-75 inches. The XL twin mattress dimensions are approximately 38-by-80 inches. Twin mattresses are moderately priced and available at virtually any retailer that sells home furnishings.
A full-sized mattress is also known as a "double." Larger than a twin mattress but not quite the size of larger mattresses, it can be considered an in-between sized mattress. The dimensions of full-sized mattress are traditionally 53-by-75 inches.
A queen-sized mattress can comfortable fit two average-sized adults. Queen mattresses are approximately 60-by-80 inches. A queen mattress is considered a large mattress, along with the king and California king mattresses. For large mattresses, split box springs come in two pieces for easy maneuvering. A split box is an option with the purchase of a queen mattress.
A king-sized mattress is approximately 76-by-80 inches and is very similar to the shape of a square, unlike smaller mattresses that are more rectangular in shape. A split box spring is standard with a king mattress.
A California king is the largest of the standard mattresses on the market, at about 72-by-84 inches. As with other large mattresses, the box spring is split to make moving it easier.