ILD Ratings

• ILD ratings are usually expressed in ranges between 10 to 16:
  10 to 12 (soft)
  13 to 15 (medium)
  16 and above (firm)
  
  

Understanding the Rating

• For the 10 to 12 range, the ILD reading indicates that it takes 10 to 12 lbs. to indent the foam by 25 percent. A higher ILD rating does not signify a better mattress; it only says the mattress is firmer.
  
  

How to Use the ILD Rating

• Use it as a guide. If you know you prefer a medium mattress, start looking at mattresses with ILD ratings of 13 to 15, but don't limit yourself to these ratings. Mattress ratings and compositions vary.
  
  

ILD and Density

• An ILD rating does not reflect mattress density. The density of a mattress relates to foam composition and determines how quickly the foam recovers or springs back into shape.
  
  

Summary

• When choosing a mattress, remember that the ILD rating is only one consideration. You will want to take density, price and comfort into account as well.