As long as it is a slightly convex mirror...ahaha
I don't hold much stock in those charts because there are too many variables to account for. Even using them as a rough guideline is error prone. I don't know why people insist on using such crude devices to determine how healthy we are or should be.
How do you feel? How do you look? Are you satisfied with those answers? These are the proper questions to answer.
If you have an insatiable need to know, then get your actual percentage through a
body impedance scale and not some very general chart provided by the insurance industry.