The Ergo Number Calculation
Your Ergo Number is derived by doing a weighted average of the various compressions that are used to make up your mattress. Each grade of foam is rated by its density, which determines the durability of the foam and its compression, which indicates its firmness. In each density range you can choose from a number of different compressions. For example, in the Koosh Natural line you can choose amongst the KN16 (soft), KN21 (medium soft), KN26 (medium), KN31 (medium firm), KN41 (firm) or KN51 (extra firm).
The last two numbers, of the part number, indicate the firmness of the foam. By multiplying the thickness of each layer you will get the total overall compression of that particular combination. Once you divide the total compression by the total thickness you will then get the average compression of the mattress. This is your Ergo Number.