The industry standard for mattress depth is 7 inches, with most offering a comfortable 10 to 14 inches. Generally, the higher the load, the deeper it needs to be. But quality is important as a well-built 10-inch mattress can be equally as comfortable and supportive as a budget 12-inch mattress. This 12.5 inch mattress gives the impression of luxury, whilst providing all the benefits of a regular mattress. With the development of the popular pillow top, depths can go up to 24 inches.