To describe your height to someone. This is the Imperial system used by the USA, and in casual conversation in many parts of the world. I know my height in Metric because that is what is printed on my drivers license, but I tend to think of height in feet and inches. Metric would be 162 cm. So if you are 162 cm tall you would say "I am five four or 5 foot 4" if you wanted to say your height in feet and inches. If people want to know they will ask "how much in feet?" or "how much is that in feet?"