Things needed - measuring tape and a book
Place book on ur head, end of measuring tape on your toe, other end should be touching the book on your head. Now, take the reading appropriately.
Measure human height by the transitive property. Stand up against the wall and make a mark at your height. Then measure the distance from the floor to the mark. You are as tall as the mark is above...
From personal experience, it is innacurate. For me I got my height measured as 5'10 at the doctors, but when I measure myself at home with a tape meter it says I am 5'9, a full 2.50cm difference.