I heard if you stand up, and spread your arms out (wingspan) that it equals your height. Is this true?
The famous artist, Leonardo Da Vinci, did a study of the ideal proportions for the human body. After all, artists are interested in getting drawings of people to look like people. He made a famous sketch of a man showing the proportions of the parts. The box around the man shows that his height equals the length of his outstretched arms from finger tip to finger tip. The center of the box is at the groin. With the arms slightly raised and the feet spread apart, a man can touch the edges of a circle where the center of the circle is at his naval. In particular, the arms are raised to the level of the top of the head and the legs are spread to form an equilateral triangle where the navel and the soles of the feet form the three corners of the triangle. Leonardo wrote: "The navel is naturally placed in the centre of the human body, and, if in a man lying with his face upward, and his hands and feet extended, from his navel as the centre, a circle be described, it will touch his fingers and toes. It is not alone by a circle, that the human body is thus circumscribed, as may be seen by placing it within a square. For measuring from the feet to the crown of the head, and then across the arms fully extended, we find the latter measure equal to the former; so that lines at right angles to each other, enclosing the figure, will form a square."
These proportions were derived from an earlier Roman writer, named Vitruvius, but it was Da Vinci who realized that the circle and the square did not have the same center. Thus Leonardo's sketch is known as the Vitruvian Man.
You have to realize that this is an idealized adult male. It definitely does not apply to children, or to teenagers while they are growing as they don't grow in proportion, but different parts grow at different times. While the proportions are pleasing to the eye, every person doesn't have exactly the "perfect" proportions. We all vary from it a bit in different ways.