Buying a too-small mattress is one of the biggest mistakes new bed-buyers make. Couples who've been sleeping on a "double" since they got married may think that's just fine, until they learn that each person has only as much sleeping space as a baby's crib! Here are size guidelines for shoppers from the Better Sleep Council:

Full beds: Sometimes still called "double," are 53 inches wide, which is just 15 inches wider than a twin size (single). That leaves each partner only 27 inches of personal space, or about the width of a crib. Both twin and full sizes are approximately 75 inches long, which may be too short for some adults, especially men.

Recommendations: Full size is only enough space for a single sleeper and only if under 5 feet 5 inches tall. Parents are increasingly choosing full size over twin for teenage bedrooms, and even for younger children in order to give parents a more comfortable place to rest when reading together at tuck-in time.

Queen beds are 60 inches wide by approximately 80 inches long – 6 inches wider and 5 inches longer than a full size mattress. These added inches can make all the difference in comfort, especially for couples, and have made the queen today's most popular mattress size. However, with 30 inches of personal space, each adult still has 9 inches less width than if they slept alone in a twin bed.

Recommendations: Queen size is a good choice for guest rooms, smaller master bedrooms and for couples who prefer close quarters. It's also a great choice for single sleepers who are also "sprawlers."

King beds are 76 inches wide by approximately 80 inches long – about 18 inches wider than a queen. This is the closest a couple can come to having as much personal space (38 inches) as each would have on a twin bed. In fact, two twin extra-long beds pushed together are about the same size, an option that can offer a flexible arrangement for a guest room.
**For consumers on the west coast, there is also the "California King," which is 72 inches wide by 84 inches long – 4 inches narrower and 4 inches longer than a regular king.

Recommendations: King size is the best choice for couples that want maximum personal sleeping space. It's also the best bet to accommodate that time on Sunday morning when children may pop into bed – or if the pets in your house have mattress privileges! However, size can be a problem. Even with a "split box spring" – two twin-size foundations to support it – to make a king set more manageable, it may be too big for some bedrooms or too bulky to navigate through some corridors, doors and stairwells. It's a good idea to break out the tape measure if there is any doubt.

Actually, you don’t need to know anything about the construction of a mattress in order to find a mattress that suits you, but you may want to know some of the following information

A. Coils: The most commonly discussed feature of an innerspring mattress is the number of coils in the mattress. This feature is also one of the most misunderstood. The main purpose of the coil unit in a mattress is support, and support is a very important component of a mattress. However, the number of coils in and of itself does not necessarily correspond to the amount of support in a mattress. The reason is that the design of the coil unit and the gauge of the wire used in the coil unit alter the total number of coils that will fit in the finite space of a mattress. So, comparing coil counts of mattresses will only have meaning if the two mattresses have the same design and the same gauge of wire.

In other words, it would be meaningful to compare the coil count of two mattresses within the same brand, but possibly not meaningful to compare two mattresses of differing brands, as the coil units will differ in design. A more meaningful look at coils would be how conforming the coil unit is to a person’s body. The best mattresses are designed to “conform to the spine’s natural curves and to keep the spine in alignment when you lay down.” (Cornell University (2000) Hotel Ergonomics - Guest Room and Office Design (Kelley Dallas)). Another important feature of a coil unit is perimeter edge support. A mattress with good perimeter edge support allows for maximum sleeping surface. An excellent edge support is a foam encased coil unit. This design also allows the mattress to be flexed more than a traditional mattress made with a border rod around the coil unit. This feature can also be a benefit if your new mattress needs to be delivered upstairs and/or around tight corners.

B. Alternatives to innerspring: There are other types of mattresses available, although innerspring mattresses are still the most common. Mattresses made completely of foam, either Memory foam or Latex foam, offer support from a foam core rather than an innerspring core. Normally, the core or center support in these mattresses is not made of Memory foam or Latex foam. Those more expensive foams are placed closer to the surface of the mattress for maximum benefit and comfort. Both Memory foam and Latex foam can also be found in the surface padding of many of the better quality innerspring mattresses. A person who is particularly sensitive to any type of pressure that might come from a coil innerspring, however, might find these foam mattresses to be best for their needs. For further discussion of these two foams used in today’s better quality mattresses, see upholstery padding.

C. Boxsprings/foundations: The primary difference between a boxspring and a foundation is flex. A traditional boxspring is designed to act as a shock absorber, and therefore has some flex in the coils of the boxspring. Some luxury brands even use 8-way hand-tie construction in some of their boxsprings, a feature mostly found in high-end sofas and chairs. Foundations, on the other hand, are designed to be a solid, inflexible surface to support the mattress. Very inexpensive mattress sets often use a wood foundation, which looks at first just like a boxspring, but upon closer examination, you will see that it is not. This type of foundation serves a purpose, but is not very sturdy and will not hold up well under the weight of kids jumping on the mattress, for example (which you know they do when you are not looking sometimes!). A modular foundation, however, found under most of today’s one-sided mattresses, is a very sturdy foundation, and provides proper support and durability. It is not recommended (and in fact may void your mattress warranty) to place a new mattress on an old boxspring. Considering the life of a mattress set is about 8-10 years, an “old boxspring” would be 2 or more years old, and/or be the wrong type of support for the new mattress.

D. Upholstery padding: The upholstery layers of a mattress are what deliver you comfort. And a mattress certainly should be a purchase based on comfort! If it has been a while since you last shopped for a mattress, one of the first things you will notice is how thick the mattresses have become. The reason is that mattresses today are made with many more layers of foam and fiber padding than mattresses from 15 years ago. All that padding is there for your comfort. The further away from the innerspring your body is, the more comfortable the mattress tends to be to most people, so mattress manufacturers have added a lot of upholstery padding to their mattresses. Two types of foam found in many of today’s luxury mattresses are Memory foam (also known as visco foam) and latex foam.

Visco Foam: Developed by NASA to absorb the tremendous forces that astronauts experience during blast-off, visco-elastic memory foam dramatically reduces pressure points. Memory foam or visco-elastic foam is temperature-sensitive, open cell foam. It continuously molds and adjusts to the shape of your body - reducing and minimizing pressure points - relieving body stress and strain.

Latex Foam: The main features and benefits of latex foam are:

* Naturally crafted from the milk of the tropical rubber tree
* Environmentally friendly – naturally derived & biodegradable
* Instantly conforms to body shape
* Provides superior orthopedic support
* Superior pressure relief reduces tossing and turning and alleviates pressure to help bring oxygen and nutrients to muscles
* Antimicrobial, dust mite and mildew resistant
* Breathable cell structure – warmer in winter, cooler in summer
* Mattresses never need turning or flipping; consistent feel from top to bottom, head to toe