Firmness of an inner spring mattress

Mattress manufacturers do lots of tricks to get “firmness”. It turns into a balancing act in which an inner spring mattress gets coils here, cushioning there, a foundation with a modest amount of give, tweaking and adjusting until you get something that works. Coil counts are a big selling point, but the truth is that some coils are made lighter than others, so their springiness isn't consistent. In fact, coil counts, whether for a simmons mattress, a sealy mattress, spring air mattress, or a serta mattress, are not a good indicator of how firm a mattress is going to be.