i have been reading for a long time and am more confused than ever. a basic question i have. if i try out a local mattress that has 3x3" layers of 100% natural dunlop with ild of 19; 26 and 36 (top to bottom) and cover x, if i purchase online the same config with the same cover x is this, without going into too much detail, more or less the same mattress? cost is high in my value equation and i can get better pricing online but am not willing to buy (hence my paralysis) without first testing locally. i did read the article related to compression modulus etc. so do i need to factor those things in. i am ver simple and am trying as best i can to say the following; i tested mattress x locally and mattress y online will be similar so in confidence i can buy the mattress online. thanks as always. could i do the same with an innerspring and latex combo?
Hi domiagnew,
If the type and blend of the latex is the same, the thickness of each layer is the same, the density of the 100% natural Dunlop is the same or very close (even if the ILD that is listed isn’t quite the same because ILD isn’t always accurate or tested in the same way with Dunlop but if the ILD is measured in the same way and is accurate then you could use ILD as well), and if the covers are “functionally similar” (a similar amount of wool, similar cotton fabric, and a similar quilting pattern) then the two mattresses would be closely comparable yes.
In most cases … a knowledgeable online supplier will give you good information and guidance about how their specific mattresses compare to some of the other very similar mattresses that are available in the market when you talk to them on the phone.
If the innersprings in both mattresses were identical and all the other layers and components were the same or very close to the same as well then you could do the same with an innerspring/latex hybrid but if the innersprings are different or if any of the latex layers are different (type and blend, firmness, and thickness) or there is a significant difference in the covers then they wouldn’t be as closely comparable in terms of PPP. Once again though … if you are trying to make these types of comparisons between local mattresses you have tested in person and a “similar” mattress that is available online then the best source of guidance would generally be a more detailed conversation with a knowledgeable and experienced online retailer or manufacturer who will know more about how their mattresses and materials may compare to other similar mattresses than anyone else.
Phoenix
thanks again. so do i only need to ask for the density for dunlop? also i assume i can also do this with a polyfoam core if i find something local to test (which has been an absolute nightmare and have still not found anything 
Hi domiagnew,
You could use ILD if the type and blend of the Dunlop is the same and the ILD is measured in the same way and is accurately described but density is often a more reliable way to make firmness comparisons with Dunlop than ILD. It will depend on how the specific manufacturers you are comparing measure firmness and on their accuracy either way.
No … polyfoam is completely different from latex and with polyfoam (or memory foam) density is a “quality/durability spec” not a “comfort or firmness spec” as it is with latex. There is more about the different specifications that can make a difference in how soft or firm a foam material feels in post #4 here and more about the different ways that one mattress can match another one in post #9 here but there are thousands of different types of materials and components and many thousands of different types of mattresses that use each of them in different combinations and designs and in most cases (with a few exceptions) … a mattress that is available locally won’t have an exact or even a similar match that is available online (or vice versa). Local testing can give you some good reference points about the types of materials and mattresses that you tend to prefer in more general terms but it won’t usually be a reliable way to know how another mattress “feels” or performs in more specific terms unless there are only very small and fairly insignificant differences between them which may be difficult or sometimes impossible to find.
Trying to use “specs” or another mattress as your “target” (instead of a common set of criteria that you can use to assess every mattress you consider) can become overwhelmingly complex and in many cases can lead to information overload or “paralysis by analysis”. In most cases with more complex mattress designs or with materials that have too many variables involved that affect how they would feel to any particular person I would avoid trying to use specs or spec comparisons as a reliable way to choose or compare mattresses.
There is more about the different ways to choose the most suitable mattress (either locally or online) and how to identify and minimize the risks involved with each of them in post #2 here.
You may be overthinking this somewhat or relying on specs that may be too complex or that you may not have enough experience to make sense of or that don’t “translate” into your own experience and I would keep your choices and your methods of choosing a mattress more simple which can also be less time consuming and frustrating.
Phoenix