The right level of firmness in a mattress is key to quality sleep. A good mattress helps you to refresh without waking up with stiffness and pain. Good sleep, in turn, helps you function well during the day. If your mattress sags in the middle, or if it is no longer comfortable to lay on even when you flip and rotate it, it's probably time to consider buying a new one.
Find the ILD rating on the mattress you are considering buying. The rating, which stands for indentation load deflection, generally varies from 12 to 50. Twelve indicates the softest mattress available and the kind you'd likely sink into, while larger numbers indicate a much firmer feel.
Pick an inner-spring mattress if firmness is one of your main considerations. A quality inner-spring mattress should properly support the shoulders, feet, head and hips. Foam-, air- and water-filled mattresses offer varied or inconsistent support depending on the density of the foam and the amount of air or water inside the product.
Sit on the mattress and then lie down on it for at least 10 to 15 minutes to measure the firmness. Lay on the mattress in the store in your usual sleeping position, whether it is on your side, back or stomach. Remember that few people stay in one position all night, so lie flat on your stomach or back and change sides to determine the comfort level in these positions as well. This enables you to judge whether the bed works for you. Lie down alongside any person who shares your bed. Although this step may seem embarrassing, this is totally appropriate and important to ensure you make the correct purchase.
Ask about a free trial. Many companies that offer quality mattresses allow a person to sleep on the mattress free of charge for 30, 60 or 90 days to try it out. This is because it often takes a week or two to become accustomed to a new mattress. Once a person realizes that the mattress is not going to be the right firmness, the window to return it often has expired.