What Is a Coil Mattress? | Springs Explained

Wondering what a coil mattress is boils down to one simple fact: the support comes from metal springs. In U.S. retail, these are often called innerspring mattresses. The coils handle support, bounce, and weight distribution, while the layers above them — foam, fiber, or quilted padding — determine how the surface feels and relieves pressure.

Coil mattresses were the original core support system in modern bedding. Some hybrids still use smaller micro-coils in the comfort layer for extra contouring, but the defining feature is always that spring-based support core.

How Coil Mattresses Work

Coils flex when you apply pressure and spring back when you remove it. That mechanical response creates the support and weight distribution that keeps your spine aligned through the night. The spring unit sits in the middle of the mattress, with comfort layers above and a base below.

The two main coil architectures are:

• Connected coils (Bonnell or open coil) — traditional interconnected springs that move together
• Pocketed coils (encased or wrapped) — each spring wrapped in its own fabric pocket, responding independently

Individually wrapped coils generally provide better contouring and motion isolation than interconnected systems, which is why most modern coil mattresses use pocketed construction.

Coil Count and Gauge: What Actually Matters

Two specs dominate coil mattress marketing: coil count and wire gauge. Coil count is the number of springs in the unit, and higher counts are often marketed for better contouring and motion isolation. Gauge refers to wire thickness — lower gauge means thicker wire and a firmer feel, while higher gauge means thinner wire and a softer, more flexible response.

Coil counts are size-dependent. A Twin and a Queen from the same model line will have different counts. Real published examples show how much they vary: the BedTech 8-inch pocket coil mattress lists 465 coils in Twin, 609 in Full, and 713 in Queen, while other models advertise 858 encased coils or 884 pocket coils in a queen size.

Higher coil counts are not automatically better. Sources consistently note that coil type and construction quality matter just as much as the raw number. A well-built 600-coil pocketed mattress can outperform a cheap 1,000-coil unit with thin wire.

Gauge alone is not a durability or comfort guarantee either. Use it as a guide for expected firmness, then check the comfort layers to understand the real feel.

What to Check Before Buying

When evaluating a coil mattress, verify three things beyond the price tag. First, confirm whether the springs are connected or pocketed — this determines motion isolation and contouring. Second, check the gauge to set firmness expectations. Third, read the comfort layer specs, since foam density and thickness heavily influence perceived firmness and pressure relief.

Edge support matters more than most shoppers realize. Many modern models use a foam-encased perimeter or reinforced border rods to keep the edges stable. Published specs from commercial mattress lines show border support rods and sidewall reinforcement listed as standard features, which tells you manufacturers treat edge integrity as a real selling point.

If you’re comparing specific models, look for the exact coil specs. Published examples from manufacturers show real differences: the Interior Resources standard line uses a 312-coil, 13-gauge unit with a 6-gauge border rod, while premium models list 884 pocket coils with 13-gauge exterior wire and 15-gauge interior wire.

One honest warning: CertiPUR-US foam certifications and non-toxic adhesive claims apply only to the specific models that carry them, not to the entire coil mattress category. Check the tag or spec sheet for the exact mattress you’re considering.

Ready to narrow down your options? Our tested roundup of the best coil mattress for side sleepers covers models that performed well in pressure-relief testing.

Common Mistakes to Avoid

• Assuming higher coil count means better — coil type and construction quality matter more
• Confusing innerspring, hybrid, pocket coil, and open coil — manufacturers use these terms differently, and some hybrids combine foam with pocketed coils
• Ignoring gauge and focusing only on count — wire thickness drives the firmness feel
• Comparing coil counts across different mattress sizes — counts are size-dependent and not comparable without context

No single coil design is universally best. Firmness and motion isolation vary substantially between models, so the right choice depends on your sleeping position and whether you share the bed.