Hi Adeline,
There is more information in post #9 here about the different ways that one mattress can “match” or “approximate” another one. Every layer and component in a mattress (including the cover) will affect the feel and performance of every other layer and component and the mattress “as a whole” so unless you are able to find another mattress that uses exactly the same type of materials, components, cover, layer thicknesses, layer firmnesses, and overall design (which would be very unlikely) then there really isn’t a way to match one mattress to another one in terms of “comfort” and PPP based on the specifications of the mattress.
Mattress manufacturers also generally try to differentiate their mattress from the mattresses made by other manufacturers and don’t normally try to “match” another mattress that is made by a different manufacturer so while you may find some local mattresses that use “similar” materials or designs and there would be many others that are in a similar general category or firmness range … they will generally have different combinations of foam layers and components.
Unless a manufacturer specifically says in their description of a mattress that one of their mattresses in the same general category is specifically designed to “match” or “approximate” another one in terms of firmness or “feel” (or they are very familiar with both mattresses and can provide reliable guidance about how they compare based on the “averages” of a larger group of people) … the only reliable way to know how two mattresses would compare for you in terms of how they “feel” or in terms of firmness or PPP would be based on your own careful testing or actual sleeping experience on both of them.
There are also no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness and some people may rate one mattress as being firmer than another and someone else may rate them the other way around. This is all relative and very subjective and is as much an art as a science.
While your own careful testing or personal experience is the most reliable way to know whether any mattress is a good “match” for you in terms of comfort and PPP or how closely it “matches” another mattress … when you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Outside of any local options that may be available to you that you can test in person … the mattress shopping tutorial includes a link to a list of the better online memory foam options I’m aware of (in the optional online step) and many of them make mattresses that are designed to approximate some of the Tempurpedic mattresses as well (including the Tempurpedic Cloud Supreme Breeze) which may also be worth talking to or considering.
Once again though … I would always keep in mind that different people will have different opinions about how closely two mattresses “match” or “approximate” each other so the options you have after a purchase to exchange or return the mattress for a refund (and any costs involved) can be a more important part of an online purchase just in case the mattress you choose doesn’t turn out as well as you hoped for.
Phoenix