Skip to content

ILD / IFD Foam Hardness

By , Editor Updated First published

Desk research from official sources. Not a product test or medical advice. How we check facts.

In short

ILD (Indentation Load Deflection) or IFD (Indentation Force Deflection) measures how hard foam feels. It uses the force needed to compress foam a standard amount. Higher ILD means firmer foam. Density (kg/m³) is separate and relates more to durability. Mattress firmness also depends on thickness, layering, and the base beneath the foam.

About 1 minutes to read

Close view of a plush velvet headboard and matching upholstered bed
Many bed words describe fabric, shape or storage — this is how they look in a room.

Definition. ILD or IFD measures the force needed to indent foam a set percentage of its thickness. It is a hardness number, not density and not mattress firmness alone.

See also firmness and sleep position and memory foam materials.