What's the minimum height of a mirror that is required for a person to be able to see their whole body?

It depends on how far from the mirror you are willing to stand. To see your whole body in a mirror when you are 0m from the mirror it would have to be as tall as you are. The smaller the mirror the further from your body it will have to be before you could see your entire body. There is no limit to how small the mirror can be as long as you can move it further away. To be functional of course, a mirror has to be much closer so a person can see the image well, which means it cannot be much smaller than the body. Which makes sense if you think logically. Most full body mirrors are almost six feet tall and we stand about two or three feet from them.