Foam mattress thickness is easy to compare as a number, but total depth does not tell you how the mattress will feel. The current All Foam mattress range includes finished constructions around 8, 9 and 10 inches deep, while the custom mattress builder lets you select whole-inch depths and layer combinations within its rules. The more useful question is not simply whether 10 inches is better than 8 inches. It is what the extra depth is made from, how the support base changes and whether the finished mattress suits the bed frame and your preferred feel.
This guide explains the practical differences between 8, 9 and 10 inch foam mattresses, how All Foam uses those depths in its standard range and what to check before choosing a custom build.
Mattress thickness is not the same as firmness
A thicker mattress is not automatically softer, firmer or better quality.
Firmness comes from the materials, indentation resistance, layer arrangement and how the mattress responds under load. Thickness determines how much material is present, but the type of foam in each layer still matters.
An 8 inch mattress with a firm support base can feel firmer than a 10 inch construction made from different materials. Equally, adding more memory foam to the top of a mattress can change the surface feel even if the support base remains similar.
The soft, medium or firm mattress guide explains why firmness needs to be judged from the full construction rather than mattress depth alone.
How the current All Foam standard mattresses compare
The three current All Foam memory foam mattresses use different total depths and support constructions.
Deep Sleeper Comfort: approximately 8 inches
Deep Sleeper Comfort has a finished depth of about 20cm. Its construction includes an Air Tech ventilation pad, 2 inches of memory foam and 6 inches of Medium Density support foam.
It is the medium-feel option in the standard range. The relatively simple 2 inch comfort layer over a 6 inch support base keeps the total mattress shallower than the other two models.
Choose it when the medium feel and this layer arrangement suit your preference, not merely because 8 inches is the lowest number.
Deep Sleeper Back Care: approximately 9 inches
Deep Sleeper Back Care has a finished depth of about 22.5cm. It uses an Air Tech ventilation pad, 3 inches of memory foam and 6 inches of High Density support foam.
Compared with Deep Sleeper Comfort, it adds an extra inch of memory foam and changes the support grade. The firmer feel comes from the construction as a whole, not from the extra inch by itself.
The product name should not be treated as a medical claim. Choose it because you prefer the firmer support profile and deeper memory foam layer.
Luxury Deep Sleeper: approximately 10 inches
Luxury Deep Sleeper has a finished depth of about 25cm. Its construction includes an Air Tech ventilation pad, 3 inches of memory foam and 7 inches of Luxury Reflex support foam.
It is the deepest standard mattress in the range. Compared with Deep Sleeper Back Care, the memory foam depth remains 3 inches while the support base increases to 7 inches and uses a different material.
This is a good example of why total mattress depth should always be read alongside layer construction.
What does an extra inch actually change?
An additional inch can be added to the comfort layer, the support base or another part of a custom construction. Those choices produce different results.
More comfort-layer depth can increase how much the upper material contributes to the overall response. More support-base depth increases the amount of structural foam beneath the comfort layers.
The All Foam custom mattress rules deliberately keep the base as the majority of the overall foam thickness. That prevents a build from becoming dominated by soft upper layers with too little support underneath.
For a 10 inch mattress, therefore, the extra depth should not simply be assumed to mean more memory foam.
Is an 8 inch foam mattress thick enough?
An 8 inch mattress can be a complete adult mattress when the materials and construction are designed for that purpose. Deep Sleeper Comfort demonstrates this with a 6 inch support base and 2 inch memory foam comfort layer.
Do not compare an 8 inch purpose-built mattress with an arbitrary 8 inch block of one foam grade. Layering, cover, ventilation components and support material all contribute to the finished product.
For custom dimensions, the builder also allows thinner mattresses where required by a particular space, but a low-profile custom foam piece has a different use case from a standard 8 inch bedroom mattress.
Why choose a 9 inch mattress?
Nine inches sits between the shallowest and deepest standard All Foam options, but the main reason to choose Deep Sleeper Back Care is its actual layer combination.
It provides 3 inches of memory foam above a 6 inch High Density support base. This produces a different surface depth and support feel from the 8 inch Deep Sleeper Comfort.
A 9 inch depth can also be useful when a customer wants a substantial mattress without raising the bed as much as a 10 inch model. The difference may sound small, but bed height affects getting in and out, headboard proportions and fitted sheet depth.
Why choose a 10 inch mattress?
A 10 inch mattress provides more total material, but the benefit depends on where that depth is used.
In the Luxury Deep Sleeper, the 10 inch total includes 3 inches of memory foam and a 7 inch Luxury Reflex support base. The extra base depth creates the most substantial standard construction in the range.
This can appeal to customers who want the deepest All Foam model and its high-firm layered feel. It is not automatically the correct choice for someone who simply thinks thicker must mean more comfortable.
Check the finished bed height
Mattress depth changes the height of the sleeping surface.
Measure from the floor to the top of the bed base, then add the proposed mattress depth. This gives you a useful estimate of the final height.
A deeper mattress can cover more of a decorative headboard, sit high against a footboard or reduce the effective height of a safety rail. On storage beds, it can also change how easy the mattress is to lift or how the finished bed looks when closed.
If you are replacing an old mattress, measure its current depth and decide whether you liked the resulting bed height before moving to a thicker model.
Fitted sheets and mattress protectors
Deep mattresses may require deeper-pocket fitted sheets and protectors. Check the stated pocket depth of your bedding rather than assuming every King or Double sheet will accommodate every mattress thickness.
Allow for the mattress protector as well. A very tight fitted sheet can compress the edges or repeatedly pull at the cover.
Bed frames, slats and support
A foam mattress should sit on a level, supportive base. The frame needs to support the complete mattress evenly and remain in good condition.
Inspect slats, centre rails and support legs before changing mattresses. A deeper mattress does not correct a bowed or broken bed base.
The UK mattress sizes guide includes practical measuring advice for frames, platforms and non-standard beds.
Mattress thickness for custom beds
The custom foam mattress builder is useful when standard dimensions do not fit the available space.
Current custom rectangular mattresses accept whole-inch thicknesses from 1 to 10 inches. Below 4 inches, the build is limited to one layer. From 4 to 7 inches, one or two layers can be used. From 8 to 10 inches, one, two or three layers can be selected.
Memory foam is only available as the top layer of a two- or three-layer mattress. The base support layer must make up the majority of the total foam thickness, with the permitted 2 inch plus 2 inch balanced construction at a total thickness of 4 inches.
These rules matter because a custom mattress should still have a coherent support structure rather than allowing every layer combination mathematically possible.
8, 9 or 10 inches for a caravan or campervan?
Space-constrained beds have different priorities. A thick domestic mattress can reduce headroom, interfere with furniture or prevent a bed platform from folding. Measure the available vertical space as carefully as the width and length. A thinner custom mattress can be appropriate where the layout demands it, but reduced depth changes the available cushioning and support. The caravan, motorhome and boat mattress guide covers these issues in more detail.
Common mattress thickness mistakes
Assuming thicker means softer: material and firmness can make a deeper mattress firmer than a shallower one.
Comparing only total depth: look at memory foam depth and support layer depth separately.
Ignoring the bed frame: a poor base can undermine any mattress thickness.
Forgetting finished bed height: deeper mattresses affect access, headboards and bedding.
Building a custom mattress with too much comfort foam: the support base should remain the majority of the construction.
Using a mattress name as a medical promise: choose from construction and feel, not a health claim implied by marketing language.
A simple 8, 9 and 10 inch comparison
Choose the 8 inch Deep Sleeper Comfort when its medium feel, 2 inch memory foam layer and 6 inch Medium Density base match what you want.
Choose the approximately 9 inch Deep Sleeper Back Care when you prefer its firmer construction, 3 inch memory foam layer and 6 inch High Density support base.
Choose the 10 inch Luxury Deep Sleeper when you want the deepest standard model, with 3 inches of memory foam and a 7 inch Luxury Reflex support base.
For non-standard dimensions or a different layer arrangement, use the custom mattress builder and choose the depth around the bed, the required support and the intended use.
The best mattress thickness is not the largest number you can fit. It is the depth that gives the construction for your bed and preferred feel while leaving enough support beneath the comfort layers. Compare what each inch is actually made from, then check the finished bed height before ordering.