When my parents bought the mattress that famously failed my 6'4" dad within a few months, the sales rep had a LOT to say about coil count. A thousand coils! Individually wrapped! What he didn't mention was the number that actually predicts whether a support core holds up: the coil gauge. Probably because "our coils are made of thinner wire than the bed next to it" doesn't close many sales.
The support core is the foundation of a mattress. Foam layers get all the attention (and to be fair, cheap foam is the most common failure — see Why Mattresses Sag), but if you're a bigger person or you plan to keep a bed for a decade, the steel matters too. Here's how to read it.
Coil gauge: the number that matters (and it's backwards)
Coil gauge measures the thickness of the wire — and it runs BACKWARDS, because this industry couldn't make anything easy. Lower gauge = thicker wire = stronger, firmer, more durable coil. Higher gauge = thinner wire = softer, more contouring, less load capacity.
Across the mattresses in the SquishMat catalog with disclosed coil specs, gauges run from 11.5 (seriously beefy) up to 19 (thin micro-coil territory), with the typical support core sitting around 13.5 to 15. Rough guide:
| Coil Gauge | Wire | What It's For |
|---|---|---|
| 12–13 | Thickest | Heavy-duty support cores, beds built for bigger bodies, reinforced perimeters |
| 13.5–14.5 | Thick | Sturdy all-around support cores |
| 15–16 | Medium | Softer-feel support cores, plush hybrids |
| 17+ | Thin | Micro-coils in comfort layers, not support duty |
If you're over about 230 lbs, I'd want the main support coils at 14 or lower, or a bed explicitly engineered for heavier sleepers. A 15.5-gauge core under a lighter sleeper is a fine design choice. Under me at 275 lbs, it's working overtime with no overtime pay.
Coil count: mostly a marketing number
Coil count isn't meaningless — a queen with 400 coils is spreading your weight across fewer, harder-working springs than one with 1,000. But past a reasonable number (roughly 800–1,000 in a queen), more coils stop buying you much, and brands know shoppers can compare counts easily, so that's the number that gets inflated. Some stack two layers of coils and quote the total. A high count of thin-gauge wire can still be a weak core. Count tells you how many workers showed up; gauge tells you how strong they are.
Pocketed vs. connected coils
Individually pocketed coils compress independently — better motion isolation (a big deal for couples, see our couples guide) and better contouring. Connected (Bonnell/offset) coils act as one grid: durable and cheap, but your partner feels every move, and comfort depends heavily on what's stacked on top. Most modern hybrids worth considering use pocketed coils; connected grids survive mostly in budget and old-school innerspring builds.
Also worth looking for: zoned coils (firmer gauge under the hips, softer under the shoulders) and a reinforced perimeter, which is what keeps the edge from collapsing when you sit on it — something us bigger folks test daily whether we mean to or not.
The part where I save you the homework
Here's the honest problem: most brands don't publish gauge at all. You get "premium wrapped coils" and a smile. We dig the actual specs into the build construction breakdowns for every mattress we catalog — coil type and gauge when disclosed, alongside every foam layer's density. And the free 2-minute quiz folds support-core strength into your SquishScore based on YOUR weight, so a core that's underbuilt for your body costs a mattress points automatically. The steel is exactly the kind of thing you shouldn't have to think about at 2am. That's our job.