Memory Foam Mattress Topper THICKNESS vs. DENSITY

I’m getting a memory foam mattress topper. But I'm debating between a few different toppers. The ones I'm thinking about are:

• 2" – 4.5 lb density
• 2" - 5 lb density
• 3" – 4.5 lb density

What is more important, thickness or density?

I would say thickness is more important. But the second most important thing is firmness or ILD (Indentation Load Deflection).

Density determines how long the memory foam mattress topper will last, but not how firm / soft it is. Many people believe that higher density means firmer, but that’s not true.
5 pound density foam can be softer than 4 pound density foam. It depends on how the foam manufacturer made it.

First you want to determine if you want a little foam or a lot. If you will be putting your topper over a firm, flat mattress, and you want a medium soft or soft feel, go with 3” or 4” of memory foam.

If you have a soft or medium soft mattress, then go with 1” or 2” of memory foam.

Memory foam firmness ratings range from 11 ILD soft, to 15ILD medium soft. Memory foam is not supposed to be firm. If you want your bed to be firm, then use a thinner memory foam topper and put it over a firmer mattress.

A word of caution: ILD ratings are not the same between different manufacturers. ILD firmness ratings measure the force of the recovery rate. In other words, it measures how hard the foam presses back when you push on it. ILD ratings were first used to measure traditional polyurethane – the base foam in mattresses and in other furniture like couches and chairs. ILD is not very accurate when applied to memory foam. So ILD ratings can vary between different manufacturers.