# How to Measure Foam Density

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Buying a mattress can be difficult, and knowing what to look for in terms of density can help you get started asking the right questions. A common misunderstanding is that the density of foam – in a mattress or pillow for example – determines its firmness. This isn't the case. A low-density foam can still be firm or hard. Density tells you the weight of the foam more accurately than the firmness. Picture a styrofoam cup for example. It's extremely thin but very firm and stiff, and you definitely wouldn't want to sleep on a styrofoam bed.

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## How to Calculate Density

To calculate the density of a piece of foam, you divide the weight of the foam by its width x height x length. If you measure in feet, density is expressed in weight per cubic foot.

Weight ÷ Width x Height x Length = Density

Say the density of a mattress is four pounds per cubic foot. This means that a cube of this mattress measuring a foot in each direction weighs four pounds. However, density isn't the only factor that will determine the comfort and firmness of a mattress.

## Why Density Matters

Remember, density doesn't equal firmness, so keep this in mind when selecting a mattress. Density does reveal the quality and durability of the mattress. A denser mattress will be heavier, so it may be more difficult to move or flip around, but it should prove to be more durable because of the increased amount of compressed material.