---
title: "ILD / IFD Foam Hardness"
description: "What ILD and IFD foam hardness ratings are and how they differ from foam density and overall mattress firmness."
url: "https://bedguide.co.uk/glossary/ild-ifd/"
category: "glossary"
primary_entity: "ILD IFD foam hardness"
date_published: 2026-08-03
date_modified: 2026-08-03
---

# ILD / IFD Foam Hardness

> 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.

**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.

Also called: indentation load deflection, indentation force deflection.

See also [firmness and sleep position](/mattresses/firmness-and-sleep-position)
and [memory foam materials](/mattresses/memory-foam).

---

Source: https://bedguide.co.uk/glossary/ild-ifd/ · BedGuide — educational encyclopedia, no affiliate commission. Facts checked against official sources where possible; see https://bedguide.co.uk/editorial-policy. Report an error: https://bedguide.co.uk/corrections.