A coil mattress, also known as a sprung mattress or innerspring mattress in the UK, is the most traditional type of mattress on the market. It uses steel coils or springs as its primary support system.
What Is a Coil Mattress? Guide to Types, Pros & Cons
SEP 09, 2026
Last updated: SEP 09, 2026
542 views, 3 mins read
Buying a new mattress that suits you doesn’t have to be a struggle. At Newentor, we’re often asked, “What is a coil mattress?” and what the difference is between open-coil and pocket-sprung coils.
To help you choose the perfect match for your sleep needs, this guide walks you through everything you need to know about coil mattresses.
In this article
What Is a Coil Mattress?
These coils form the mattress core and are responsible for providing structural integrity, push-back support and overall durability. Thin layers of foam, fabric or other padding materials are placed on the top and bottom of the coil system for cushioning, but the coils remain the dominant functional component.
Coil mattresses have been a staple of the bedding industry for nearly 100 years and are widely recognised for their bouncy, responsive feel—often described as sleeping “on top” of the mattress rather than “sinking in”.
Key Features, Pros and Cons of a Coil Mattress
Coil mattresses are categorised by how their springs are constructed and connected. The four primary types are Bonnell (open) coils, offset coils, continuous coils, and pocket sprung (encased) coils. Each type offers distinct features, pros and cons in terms of support, motion isolation, contouring and price.
Mattress Coil Types at a Glance
| Coil Type | Construction | Key Features | Typical Use |
|---|---|---|---|
| Bonnell (Open) Coils | Hourglass-shaped, interconnected by spiral wires. | Oldest design; affordable; very bouncy; poor motion isolation; least pressure relief. | Budget mattresses, spare beds, older-style innersprings. |
| Offset Coils | Hourglass-shaped with flat wire ends; hinged effect. | Better contouring than Bonnell; reduced motion transfer; hinged pivot points. | Mid-range innerspring mattresses; improved comfort. |
| Continuous Coils | Formed from a single continuous wire creating rows of coils. | Stable; durable; good support; less adaptable to zoning. | Traditional innerspring mattresses; cost-effective construction. |
| Pocket Sprung Coils | Each coil is individually wrapped in fabric. | Excellent motion isolation; superior contouring; reduced noise; more expensive. | Modern hybrids, luxury hotel beds, premium mattresses. |
1. Bonnell (Open) Coils
Bonnell coils are the oldest and most traditional coil design. They are instantly recognisable by their hourglass shape, which is narrow in the middle and wider at the top and bottom. These coils are interconnected by a network of spiral wires, creating a single, unified spring unit.
Pros
- Most affordable coil option.
- Highly durable and robust.
- Very responsive and bouncy.
Cons
- Significant motion transfer (movement travels across the bed).
- Limited pressure relief and body contouring.
- Can sag more quickly than other types.
Bonnell coils are most commonly found in budget-friendly mattresses, older models and spare room beds.
2. Offset Coils
Offset coils are a refinement of the Bonnell design. They retain the hourglass shape but feature flat wire ends (portions of the wire that are flattened) at the top and bottom. These flat sections allow the coils to be hinged together, creating a pivot effect.
Offset coils are often found in mid-priced innerspring mattresses and models that prioritise improved comfort without the cost of full pocketing.
Pros
- Better body contouring than standard Bonnell coils.
- Reduced motion transfer due to hinged connections.
- Improved durability at pivot points.
Cons
- More expensive than Bonnell coils.
- Still interconnected, so motion isolation is not as strong as pocket sprung coils.
3. Continuous Coils
Continuous coils are constructed from one very long, single wire formed into a series of coils that run the length of the mattress. Each row is made from this single wire, and rows are interconnected. This design creates a stable, unified support structure.
Pros
- Excellent stability and strength.
- Reduced side-sway and roll-off feeling.
- Consistent support across the surface.
Cons
- Difficult to zone or customise firmness in specific areas.
- Less common in modern premium mattresses.
- Motion transfer can easily disturb the sleep of a bed partner.
4. Pocket Sprung Coils
Pocket sprung coils, also called wrapped coils or encased coils, represent the most advanced and popular coil technology in contemporary mattresses. Each individual steel coil is separately wrapped in a fabric or non-woven material pocket. These pockets are then glued or compressed together to form the mattress core, but the coils themselves remain mechanically independent.
This ensures that even if one person turns over on one side of the mattress, it will not disturb the person on the other side. Current pocket sprung technology has evolved to produce zoned mattresses, meaning a single mattress can provide varying levels of support for different parts of the body.
This technology was developed to alleviate back pain and helps maintain spinal alignment. The finer the zoning, the more the mattress conforms to the body’s curves.
Generally, most pocket sprung mattresses on the market have 3 or 5 zones. The Newentor Halcyon Series hybrid mattress uses 3 different types of pocket-sprung coils, providing a 7-zone pocket-sprung system to achieve 3 types of softness and contour to your head, shoulders, waist, hips, thighs, lower legs, and feet.
In addition, it is equipped with a dual-layer spring system. On top of the 7-zone pocket sprung system, there is a 1.00mm micro-coil layer that is so soft and comfortable it feels identical to the memory foam comfort layers in most mattresses, without the heat dissipation problems or the sagging that occurs over time with foams.
Pros
- Superior motion isolation: Movement on one side is not felt on the other—ideal for couples.
- Enhanced contouring: Each coil responds independently to pressure, conforming to the body’s curves.
- Better spinal alignment: Individualised support for shoulders, hips and lower back.
- Quieter operation: Fabric wrapping eliminates metal-on-metal friction.
Cons
- Higher cost.
Pocket sprung coils are the hallmark of hybrid mattresses and are widely used in luxury hotel beds and premium home mattresses. They are often combined with memory foam, latex or gel-infused foam comfort layers to balance support with pressure relief.
Pocket Sprung vs Open Coil vs Memory Foam Mattresses
Comparison at a Glance
| Feature | Open Coil | Pocket Sprung | Memory Foam |
|---|---|---|---|
| Construction | Interconnected wire springs. | Individual fabric-wrapped springs. | High-density viscoelastic foam. |
| Support | Firm, “one-piece” feel. | Zoned, adaptive support. | Deep contouring/cradling. |
| Motion Isolation | Poor | Good | Excellent |
| Cooling | Excellent (high airflow). | Good (breathable). | Fair (tends to retain heat). |
| Durability | Average (prone to sagging). | High. | High (if high-density). |
| Price Range | Budget-friendly. | Mid to high-end. | Varies widely. |
| Ideal For | Budget, spare rooms, hot sleepers, firm feel. | Couples, back pain, combination sleepers, zoning needs. | Side sleepers, joint pain, motion isolation priority. |
Which One Is Best for You?
1. Open Coil (The Traditional Choice)
- The Feel: Bouncy and very firm. Because the springs are clipped together, the entire mattress reacts as one unit.
- Best For: Spare rooms, children’s beds, or shoppers on a strict budget.
- The Downside: It has the shortest mattress lifespan, and the centre of the mattress is prone to sagging.
2. Pocket Sprung (The Crowd Favourite)
- The Feel: Responsive but controlled. Since each spring moves independently, the mattress shapes itself to your body’s curves (shoulders and hips) rather than pushing back uniformly.
- Best For: Couples (due to low motion transfer) and those who want support without the “sinking” feeling of foam.
- The Downside: High-quality pocket sprung mattresses are more expensive than standard open coil models.
3. Memory Foam Mattress (The Pressure Reliever)
- The Feel: A “hug-like” sensation. It uses your body heat to soften and mould to your exact shape, providing excellent pressure relief for joints.
- Best For: Side sleepers, people with chronic joint pain, and light sleepers who are easily disturbed by a partner’s movements. Some memory foam mattresses now even allow you to adjust the firmness by rearranging the different foam layers.
- The Downside: Memory foam can retain heat, may have an initial odour (off-gassing), and some people find it too hugging or difficult to move around on.
FAQs About Coil Mattresses
1. What is a good coil count in a mattress?
Coil count refers to the total number of springs in the mattress. While counts vary by size, here are the industry standards for a high-quality bed:
- Single (90 x 190 cm): 600 – 900 coils.
- Double (135 x 190 cm): 800 – 1,200 coils.
- King Size (150 x 200 cm): 1,000 – 1,500 coils (Industry benchmark).
- Super King Size (180 x 200 cm): 1,200 – 1,800 coils.
2. What should I look for in a coil mattress?
Beyond the count, pay attention to these three technical factors to ensure the mattress meets your needs:
- Coil Gauge: This determines firmness. A lower gauge (12–13) means thicker, firmer wire. A higher gauge (14–15) means thinner, bouncier wire.
- Coil Type: Pocket sprung coils are generally superior for couples because they isolate motion. Bonnell or Continuous coils are better for budget-friendly, very firm support.
- Edge Support: Look for mattresses with a reinforced perimeter of thicker coils or high-density foam around the edges. This prevents the “rolling off” feeling when you sleep near the side.
3. How long does a coil mattress last?
On average, a coil mattress lasts 7 to 10 years, depending on the materials used:
- Traditional Innerspring: Can last 5–7 years before the metal begins to fatigue.
- Hybrid Mattresses: Combining pocket sprung coils and memory foam, these often last around 8–10 years.
4. Do coil mattresses sag?
Yes, all coil mattresses will eventually sag due to natural wear and tear over time:
- Metal Fatigue: Over years of supporting weight, the steel coils lose their “rebound” and stay slightly compressed.
- Comfort Layer Wear: The foam layers on top of the coils can wear out, leaving permanent “body impressions” or dips in the surface.
5. What’s inside a mattress?
A mattress is essentially a layered “sandwich” designed for comfort and support.
The Support Core (The Foundation)
This is the thickest, bottom layer that determines firmness and durability.
Common materials used:
- Coil Springs: Uses steel coils (often individually pocketed) for bounce and airflow.
- Foam: Made from high-density polyurethane foam for a solid, quiet base.
- Latex: Durable and resilient, often with an open-cell structure for breathability.
The Comfort and Transition Layers (The Feel)
These sit on top of the core and provide pressure relief.
Common materials used:
- Memory Foam: A heat-sensitive foam that contours slowly to your body.
- Polyfoam: A lighter, more responsive foam used for cushioning.
- Latex: A bouncy, responsive material that offers pressure relief with a springy feel.
- Micro-coils: Very small springs that add targeted support and airflow.
The Cover (The Package)
The outer fabric is usually a blend of cotton, polyester or wool. It may include a thin layer of foam quilting for initial softness.
In short: Coils or foam provide the support, while the materials above them provide the comfort. Understanding this helps you choose a bed that suits your sleep style.
Final Thoughts
In summary, coil mattresses vary based on their spring systems. Hybrid mattresses, featuring advanced pocket sprung technology, have become the top choice for many by perfectly balancing comfort and support.
If you’re looking for a better sleep experience, the Newentor Halcyon Series hybrid mattress is an excellent option.
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