Twin (or Single) — 39" x 75"
Most common for children's rooms, daybeds, trundle units, and hideaways. Approximate width per person: 39".
Twin XL (or Twin Extra Long) — 39" x 80"
Is generally used in college dorm rooms and is 5" longer than standard twin size. Bedding may be harder to find and available only a limited variety of styles. Approximate width per person: 39".
Full (or Double) — 54" x 75"
Full-size beds are 15" wider than twin beds. This won't leave much elbow room for 2 adults (each will have only 27" of width vs. 39" in a twin bed). Also, a full bed is only 75" long which may be too short for some adults. But, this size is a good option for a guest room or as a child's step-up mattress. Approximate width per person: 27".
Full XL (or Full Extra Long) — 54" x 80"
Full XL size beds are 5" longer than regular full beds. Bedding may be harder to find and available only a limited variety of styles. Approximate width per person: 27".
Queen — 60" x 80"
Currently, the dominant size bed in America, queen beds are 6" wider (and 5" longer) than a full-size bed. These added inches can make all the difference in comfort, but each adult still has 9" less than the width of a standard twin bed. However, it's a good choice for guest rooms and smaller master bedrooms. Can use standard pillows or the slightly larger queen size pillows. Approximate width per person: 30".
King (or Eastern King) — 76" x 80"
King beds are growing in popularity. King is about 16" wider than a queen bed. Both are about 80" long. The eastern king is the only bed to give each person the same width as a twin bed. In fact, you can push 2 extra long twin beds together to be the same size as an eastern king. This is a good way to have a versatile guest room (use 2 twins separately or push together to make a king bed for couples). An eastern king bed comes with one mattress and two half-width box springs to be more manageable when moving. Approximate width per person: 38".
California King (aka Western King) — 72" x 84"
California King is 12" wider than a queen bed but adds 4" in length. This may be a better choice for taller adults. California king bed sets come with one mattress and two half-width box springs to be more manageable when moving. Approximate width per person: 36".