An innerspring mattress’s firmness comes primarily from its comfort system, while its core plays a bigger role in support. For side sleepers, a typical range is soft (3) to medium (5); body weight can affect feel. Pocket coils contour more closely and may help partners avoid waking each other; continuous-wire coils do not provide contouring.
Firmness is different from support: firmness describes how hard or soft the surface feels, while support concerns whether the mattress promotes proper spinal alignment. Sleep Foundation says the comfort system is primarily responsible for firmness, while the core plays a bigger role in support.
When comparing an innerspring, ask about surface feel separately from spinal alignment. Then ask what the comfort system contributes to firmness and what the core’s role is in support, instead of treating firmness and support as interchangeable. This separates the feel you notice at the surface from the part of a mattress that plays a bigger role in support.
Comfort layers are a practical place to compare feel because the comfort system is primarily responsible for firmness. Softer layers contour and cushion pressure, while firmer layers help prevent sinkage and hold the spine aloft with subtle contouring.
Comfort layers
Thickness is useful only when you know whether a figure describes the whole mattress or the comfort system.
Sleep Foundation says most mattresses are 10 to 15 inches thick overall, while comfort layers generally measure 1 to 5 inches.
Most medium-firm mattresses have a comfort system measuring 2 to 3 inches thick, which is a layer measurement rather than total mattress height.
Compare overall thickness and layer thickness separately when reading a product listing, since the ranges describe different parts of the mattress.
Checking foam-free materials
LifeKind identifies the Traditional as its only latex-free option.
The maker describes the Traditional as fully upholstered in a GOTS-certified organic cotton and wool quilted cover and as flippable for lasting comfort and durability.
A latex-free label does not answer every material question, so check the individual model description for the construction you want.
Firmness labels help compare feel, but they are not standardized measurements. Sleep Foundation describes ratings from 1 to 3 as quite soft and says they may also be called plush; most mattresses rate around 5 or 6. A medium from one brand may be closer to another brand’s firm than to its medium.
Before comparing a soft, medium, or firm innerspring, check which ratings or definitions the maker provides. A matching label alone does not mean mattresses feel alike, so use the brand’s definition along with any rating scale.
Body weight can affect how an innerspring feels: the same mattress is likely to feel softer to a heavier sleeper and firmer to a lighter sleeper. For side sleepers, Sleep Foundation’s typical range is soft (3) to medium (5).
If you are choosing a softer coil mattress as a side sleeper, compare options across that range rather than relying on the word soft alone.
Consider how your own weight may affect the feel, since the same mattress can feel different to heavier and lighter sleepers.
Pocket springs contour more closely to the body and move only when pressure is placed directly on them. People who share a bed are less likely to wake their partners on a pocketed-coil mattress.
Tom’s Guide describes continuous-wire coils as durable and cheap, but says they do not provide contouring.
Check whether a model uses pocket coils or continuous wire if close contouring matters, because the descriptions differ on contouring.
Ask whether the coils move independently under direct pressure when checking a pocket-spring model.
Nest Bedding describes a split king as two Twin XL mattresses side by side, and a king with internal split firmness as one connected mattress with a different comfort-layer feel on each side.
Setup
Mattress arrangement
Feel
Split king
Twin XL pair side by side, standard king-size footprint
Separate mattress for each sleeper
Internal split
One connected mattress
Different comfort-layer feel on each side
For partners comparing different feels, check the setup to see whether it uses separate mattresses or one connected mattress with an internal split.
Consumer Reports says a 3-inch foam topper or a feather topper may make a mattress feel softer and more comfortable. When comparing this option, check the material and thickness, and keep the source’s “may” in mind rather than treating a softer feel as certain.
The RTI study evaluated mattresses in participants’ homes for approximately 4 weeks per mattress. That describes the study’s test schedule, not a general rule for buyers about how long every buyer must test a mattress.
Brooklyn Bedding estimates that a new mattress typically takes around 30 to 45 nights to break in, with the same amount of time for the body to adjust to its sensation. Treat that as the maker’s estimate, not a guaranteed timeline for every innerspring.
Firmness labels are descriptions, not measurements. Furniture in Fashion says a medium from one brand can be closer to another brand’s firm than to its medium.
This IKEA listing cannot show whether firm coil mattresses cost less. For a specific model, check prices across firmness options at the same size. IKEA lists the VESTERÖY pocket-spring mattress, firm/white, Queen, at $299.
Can one mattress have a different feel on each side?
An internal split king can offer a different comfort-layer feel on each side while remaining one connected mattress. Nest Bedding says Sparrow and Owl offer multiple Twin XL firmness choices, so partners can select different feels within the same construction.
We read 14 published pages from 11 sites (Sleep Foundation, tomsguide.com, lifekind.com, furnitureinfashion.net and 7 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.