Mattress & Sleep Glossary

The thickness of the wire used to make pocketed or innerspring coils, measured on the inverse American Wire Gauge (AWG) scale. Lower gauge = thicker wire = firmer support.

The number of individual support coils inside a mattress, measured at Queen size. More coils typically means more responsive support — but only if the coils are properly engineered.

Support coils individually wrapped in fabric pockets, allowing each coil to compress independently. Standard construction for modern hybrid mattresses.

A traditional mattress construction using interconnected steel coils as the support core, typically topped with thin foam or fiber padding.

A mattress combining a pocketed-coil support core with foam, latex, or polymer comfort layers. The fastest-growing mattress category over the past decade.

Construction that varies firmness along the length of the mattress — typically softer at the shoulders, firmer under the lumbar and hips — instead of using one uniform surface.

The upper section of a mattress — everything above the support core — that determines surface feel, pressure relief and how firm the bed reads on day one.

A measurement of how firm a foam is, expressed as the pounds of force required to compress a 4" foam sample by 25%. Higher ILD = firmer foam.

The weight per cubic foot of a foam sample, measured in lb/ft³. Higher density = more material = more durable foam (but heavier and more expensive).

Two manufacturing processes for latex foam. Dunlop is denser, firmer, and more durable; Talalay is lighter, softer, and more breathable. Both are derived from natural rubber tree sap.

A viscoelastic polyurethane foam that responds to body heat and pressure, slowly conforming to body shape and rebounding slowly after pressure is removed.

A natural or synthetic foam made from rubber tree sap (or petroleum-derived alternatives). More responsive, more durable, and more breathable than memory foam.

A general-purpose foam used as transition and support layers in nearly every modern mattress. Cheaper and more variable in quality than memory foam or latex.

The release of volatile organic compounds (VOCs) from new mattress materials, producing a temporary chemical smell after unboxing. Typically dissipates within 1–7 days.

A certification program that tests polyurethane foams for harmful chemicals, low VOC emissions, and durability. Standard certification across nearly all reputable foam mattress brands.

An independent textile certification verifying that fabrics are free from harmful substances. Common on premium mattress covers, sheets, and pillow fabrics.

The leading certification for organic latex foam, requiring 95%+ organic raw material content and verifying ethical sourcing, processing, and labor practices.

The leading certification for organic textiles (cotton, wool), requiring 95%+ organic fiber content and rigorous standards on processing chemicals and labor conditions.

A class of cooling materials embedded in mattress covers and comfort layers that absorbs body heat during temperature transitions, keeping the surface measurably cooler.

A material property combining viscosity (resistance to flow) and elasticity (ability to return to shape). Memory foam's defining characteristic — it deforms slowly under pressure and rebounds slowly when pressure is removed.

The weight of a fabric per square metre. The most reliable single spec for bedding density, used for sheets, towels and mattress covers where thread count is unhelpful.

A mattress's ability to absorb partner movement so it doesn't transfer across the surface. Critical for couples, especially when one partner is a light sleeper.

How firm and stable a mattress feels when sitting or sleeping near the perimeter. Important for small bedrooms (where you sit on the bed to dress) and for couples sharing the full sleeping surface.

The standard 1–10 mattress firmness rating, where 1 is extremely soft (deep sinkage), 10 is extremely firm (almost no give), and 6 is the medium-firm sweet spot for most sleepers.

How far a body or a calibrated weight sinks into a mattress surface, measured in inches. The single most useful lab number for predicting whether a bed will suit your body weight.

How well a mattress spreads body weight so no single contact point carries enough load to restrict blood flow. Measured in millimetres of mercury (mmHg) of peak surface pressure.

A mattress's ability to move body heat and moisture away from the sleep surface so core temperature can fall the 1–2°F that sleep onset requires.

How long a surface takes to return to its original shape after pressure is removed, measured in seconds. Determines how easy the bed is to move around on.

A risk-free in-home trial period offered by mattress brands, typically 90–365 nights, during which buyers can return the mattress for a full refund.

The brand's coverage period for manufacturing defects and excessive sagging, typically 10 years to lifetime. Covers structural defects but not normal comfort changes.

A mattress compressed, roll-packed and vacuum-sealed for shipment in a single carton, then expanded by the buyer at home. The dominant direct-to-consumer format since the mid-2010s.

A paid or included service where a delivery team brings the mattress into the bedroom, sets it up on your frame, and usually removes the old one.

Warranty coverage where the manufacturer pays a declining share of repair or replacement cost as the mattress ages, with the owner covering the rest.

A foundation is a rigid, non-flexing platform base; a box spring contains actual springs that flex under load. Modern mattresses almost always require the former.

Keeping the spine in the same gentle S-curve while lying down that it holds while standing with good posture. The primary orthopedic goal of any mattress purchase.