As you can see from the picture, it is not 13 inches, it did not even expand to 12 inches. I am kind of disappointed with that, as I really wanted my mattress to be at least 12 inches thick, and I measured it at its thickest area. Instructions were followed and mattress was allowed to expand on a flat surface for 48 hours. The smell was not bad, it aired out pretty quickly. However, it is pretty comfortable, it is soft and yet firm. Hopefully it lasts longer than our last mattress, which was much more expensive. It still feels like a good quality mattress considering it came out of a box.