Why a Dormeo Double Mattress Mattress Is a Good Choice A double mattress in sale mattress is a good option for anyone who needs an extra large bed that can comfortably sleep more than one person. It's also great for guest rooms or kids bedrooms. Doubles like single-sided mattresses are designed to be turned frequently so that each side gets an opportunity to rest. This prolongs each side's life which means you'll require less maintenance. Size It isn't easy to determine what size mattress you should purchase, whether you are seeking a new one or just an upgrade. There are a variety of factors to be aware of, such as your budget and preferences. Once you have a good idea of your particular bedroom needs and preferences, you can narrow your options and choose the right mattress for you. The standard American bed size is 39 inches by 75 inches or "twin" for one adult. It is a tiny size that can only accommodate one adult.