Twin

Also known as a "single" mattress. Great in children's rooms and smaller bedrooms. A narrow bed that is easy to move and fits almost anywhere.
Approx. width per person: 39"

Pros: Fits in smaller bedrooms. Sheets are less expensive than for other sized beds.

Cons: Too short for many adults.

Twin XL

Five inches longer than the standard twin and typically used in college dorms. Easy to move from room to room and great for taller teens.
Approx. width per person: 39"

Pros: Longer length is great for taller teens and adults.

Cons: Bedding can be harder to find and available patterns may be limited.

Full

Sometimes called a "Double" mattress. Wider than a twin, but still limits sleeping space for two adults.
Approx. width per person: 27"

Pros: Fits into smaller rooms. Sheets are less expensive than queen or king size.

Cons: Considered by many to be too narrow for two adults. At 75" in length, may be too short for some.

Queen

Longer and wider than a full, a queen is more accomodating for two adults. A good choice for smaller master bedrooms.
Approx. width per person: 30"

Pros: Better fit for two adults. Plenty of length for most adults. Bedding is easy to find.

Cons: Only slightly more sleeping width per person than a full. Some bedding is sold as "Full/Queen" and may not perfectly fit either size.

King

Sometimes referred to as an "Eastern King" and offers the same width per person as a twin. A king mattress uses two twin extra long sized box springs.
Approx. width per person: 39"

Pros: Widest standard bed available. Comfortably sleeps 2 adults. Sheets are easy to find.

Cons: Large size makes it difficult to fit up stairs and into smaller rooms. Bedding is more expensive than other standard sizes.

California King

Also known as a "Western King" mattress. This may be the preferred choice of taller adults and adds a foot in width and four inches in length to the standard queen.
Approx. width per person: 36"

Pros: More length to accomodate a taller person. Ample width for two adults.

Cons: Challenging to move up and down stairs and from room to room. Bedding is expensive in king sizes. Sheets are more available on the West Coast and may be difficult to find in other parts of the country.