What is Pound Density and ILD/IFD Ratings in Regard to Memory Foam?

The lb (pound) density of memory foam is simply a measurement of the weight of a cubic foot (volume of a cube with sides of 1 foot in length) of the material. So, for instance, a 4 lb density memory foam topper pad (like we sell) is 4 lbs per cubic foot of foam. Basically, memory foam is made from polyurethane with added chemicals that add to its viscosity or resistance, which increases its density. The hardness or softness of memory foam plays a key role in determining comfort. Its firmness is determined by its ILD/IFD rating. Indentation Load Deflection (ILD) or Indentation Force Deflection (IFD) measures the amount of force, in pounds, required to indent an 8 inch diameter disc into a measured visco-elastic foam sample and make a 1 inch indentation. This is commonly known as ILD/IFD at 25% compression. ILD/IFD ratings for memory foam typically range from 10 (super soft) and 120 (semi-rigid). Most memory foam mattresses range between a 12 to 16 ILD/IFD. Our memory foam topper pads are a 4 lb density, with an ILD/IFD of 10. Our mattress memory foam layers are a 3.2 lb and 3.4 lb densities, respectively.

For more information on our mattress,see our Memory Foam Mattress Page.