If you are in the market to purchase a memory foam mattress, it is important to take firmness into consideration besides thickness and density. This will greatly impact of the experience you have with your memory foam mattress and whether your venture is a positive one.

The firmness in memory foam mattresses is calculated by its Indentation Load Deflection (ILD) rating. An appropriate ILD range is between 10 and 17. If the ILD is too low or too high it will compromise one of the memory foams most sought after features, the ability to contour to your body. An ILD to 12 is normally considered to be soft, while an ILD in the range of 13 to 15 would be considered normal, and a firm mattress is considered 16 and above.

Since ILD numbers may vary among manufacturers and are not always considered to be a guaranteed indicator of firmness, it is important to know what ILD means and how it can affect the experience you have with your memory foam mattress.

The ILD of a memory foam mattress boils down to the pressure resulting when a segment of foam is pressed down about 25 percent. In other words, if you have a mid-range memory foam mattress between 13 and 15 ILD, then it would take 13 to 15 pounds of pressure to indent the foam by 25 percent.

As mentioned above, a lower ILD rating normally indicates a softer memory foam mattress, while a higher rating is indicative of a mattress that is firmer. It is important to remember when purchasing a memory foam mattress, unlike the innerspring mattress, firmness cannot be the deciding factor. Firmness should certainly be considered, but thickness and density needs to be as well. All three of these components together are what is going to make the memory foam experience a positive one.