Sinuous springs are a continuous, S-shaped steel-wire system, while pocketed coils respond to pressure placed directly on each coil. Sinuous springs are generally used in upholstery and bedding; pocketed coils can contour more closely. Compare mattress layers, not spring count alone; pocketed coils can respond without transferring motion to surrounding coils, while continuous-wire coils may still transmit some movement.
Sleep Foundation describes continuous coils as rows of loose coils formed from one wire and linked by helical wires; continuous-wire support cores generally contain less metal and cost less to produce.
Sinuous Springs
Sinuous springs are generally used in upholstery, bedding, and car-seat manufacturing.
Sinuous springs are a continuous, S-shaped steel-wire system used in sofa seat and back frames.
Pocket Springs
Which? found that a higher pocket-spring count did not automatically provide better support in its tests.
Compare the spring count with the listed layers, rather than treating the number as the whole mattress.
For pocket-spring firmness, check coil count, wire gauge, and spring pre-tension.
Sleep Foundation says pocketed coils respond to pressure placed directly on each coil.
Tightly connected continuous-wire coils may still transmit some movement when responding to pressure.
Which? notes that a pocket-sprung mattress won't necessarily mould to your shape like memory foam, although its springs are designed to respond to body shape.
The Consumer Council says a mattress that is too firm cannot conform to body curves and can increase pressure at the shoulders and hips.
Pocketed coils contour more closely to the body because each responds to pressure placed directly on it. They can also respond to movement without transferring it to surrounding coils, while linked continuous-wire coils may still transmit some movement. The Consumer Council's double-mattress test measured vibration in individual models and found different results.
Test example
Finding
Interlocking spring
1 model had the worst vibration performance in double-person mode
Pocket spring
1 model had the highest stability with vibration-absorbing materials and scored 5 points
Sleep Foundation describes “this straightforward design” as highly durable and inexpensive. Pocketed coils' more complex construction often commands a premium price. Which? tested pocket-spring mattresses priced from under £200 to over £2,000.
Some pocket-spring mattresses lose height as their layers compress with age, and spinal support is affected in some cases. A study found that dipping decreased as internal material thickness increased, and that dipping and durability factors vary with material presence, thickness, and elastic performance.
For a warranty measurement, an indentation can be measured at its deepest point.
For a warranty measurement, keep the bed unweighted while measuring.
For a warranty measurement, place a straight edge across the mattress, then measure the deepest point of the indentation.
An excellent mattress is more likely to result from layers working together than from spring number or configuration alone; internal materials, coil details, edge support, and sleeper fit also relate to durability, firmness, or support. Avocado’s zoned design is one example of how a mattress may vary support and pressure relief; internal-material thickness and elastic performance also affect dipping and durability.
Which? recommends considering how the layers work together rather than relying on spring number or configuration alone.
For pocket-spring firmness, compare coil count, wire gauge, and spring pre-tension.
Check for perimeter reinforcement; some manufacturers add low-gauge coils around the edge to strengthen edge support.
Avocado describes its zoned design with its firmest 14-gauge coils through the hips and lumbar for support, and softer coils at the shoulders for pressure relief.
When judging support, consider body weight, weight distribution, and sleep position.
Pocketed coils can respond to movement without transferring it to surrounding coils. In the Consumer Council's double-person test, 1 interlocking-spring model had more vibrations, meaning a person will be more easily affected when the other person turns or moves.
In that test, 1 pocket-spring model with effective vibration-absorbing materials had the highest stability and scored 5 points.
The cited descriptions do not establish whether sinuous springs and continuous coils are the same design. Continuous coils are described as rows of loose coils formed from one wire and connected by helicals; continuous-wire designs are also described as individual wires spanning the mattress and connected by helicals. One maker also calls zig-zag springs “Sinuous.”
The cited sources do not establish that pocket springs are always more comfortable. Which? says a pocket-sprung mattress won’t necessarily mould to your shape like memory foam, and tested models priced from under £200 to over £2,000. Mattresses that are too firm cannot conform to body curves and can increase pressure at the shoulders and hips.
Does a higher pocket-spring count mean better support?
In Which?’s tests, more springs did not mean better support; mattresses with 111 to 826 springs/sq m showed wide variation in performance, and coil count, wire gauge, and spring pre-tension affect firmness. Consumer Reports cautions that more coils may be made with thinner-gauge metal. Sleep Foundation says metal quality, tempering, coil height and gauge, shape, and turns also affect how firm and supportive coils feel.
The cited study does not establish whether pocket springs themselves soften over time; it says the factors affecting mattress dipping and durability vary with internal materials' presence, thickness, and elastic performance.
We read 13 published pages from 10 sites (soisu.com, Sleep Foundation, zigzagsprings.com, which.co.uk and 6 more), checked in October 2026. Every sentence in the answers above cites one of them; the offer card at the end names its own source. This page reports published sources only; we did not test mattresses in person.