The amount of force required to compress a foam specimen by a given % over the entire top area of the specimen. Usually expressed in pounds per square inch.

This is one way of measuring the softness or comfort level of a sponge mat. It measures how much a person's foot sinks into the mat– the higher the reading, the softer the mat. The results are affected by the thickness of the sponge backing and the flexibility of the surface material. We consider .20 - .5 the ideal range. The test is ASTM D575.