Coil Gauge
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.
Coil gauge is one of the two most important specs on any innerspring or hybrid mattress (the other is coil count). The gauge number describes the wire's thickness using the inverse AWG scale: a 12-gauge coil is THICKER than a 15-gauge coil, despite the smaller-sounding number.
Typical residential mattress coils range from 12-gauge (very thick, very firm — used in support cores for heavy sleepers and crib mattresses) to 17-gauge (thin, soft, bouncy — used in comfort layers and budget mattresses). Most quality hybrids use 14-gauge or 15-gauge coils.
A mattress can layer multiple gauges to fine-tune feel: a 13-gauge perimeter coil array for edge support, a 15-gauge interior for body conformity, and a 14-gauge zoned lumbar section for back support. This is sometimes called 'zoned coil construction'.
Coil gauge interacts with coil count and coil height. A 14-gauge coil at 6" height feels different from a 14-gauge coil at 8" height — the taller coil compresses more under the same load. Comparing gauge alone without context can mislead.
In our own teardowns the gauge printed on a spec sheet often describes only the support core, while the transitional or micro-coil layer above it runs two to three gauges thinner. That is not deceptive on its own, but it means two mattresses both advertising '14-gauge coils' can feel completely different once you lie on them. Ask which layer the number refers to before you treat it as comparable.
Gauge also predicts how a mattress ages rather than how it feels on night one. Thin wire loses tension gradually, so a 16-gauge core sleeps pleasantly soft for a year and then develops the shallow body impression owners describe as 'a hammock in the middle'. If a brand will not publish gauge at all, treat the omission as information: manufacturers using thick wire almost always advertise it.
What This Means for Shoppers
If you weigh over 230 lb or share a bed with a partner who does, look for a support core gauge of 13 or 14 — anything thinner (15 or 16) will sag faster. For lightweight sleepers under 150 lb, a 15-gauge core is comfortable and durable.