PENIS LENGTH
Penis length is defined as the linear distance along the dorsal side of the erect penis extending from the mons veneris to the tip of the glans.
In non-medical terms, penis length is measured in a straight line on the top side of the erect penis, from the skin of your belly to the tip of your penis.
Penis circumference is defined as the linear distance around the widest, thickest, part of the erect penis.

 

HOW TO MEASURE YOUR ERECTION
1. Stimulate yourself into an erectile state.

2. Place a ruler on the skin of your belly, at the base of your erect penis. While technically you should not push it against the skin, some of the studies used in this guide allowed the measurer to push it to the bone beneath the skin (pubic bone), so if you want to you can.
3. Press the ruler against your penis and read the nearest quarter-inch measurement at the tip of your penis.
4. Record this number on a piece of paper.
5. Repeat this measurement two more times, preferably with different erections and preferably on different days as penis size will differ depending on the level of arousal, time of day, room temperature, and recent sexual activity.

PENIS CIRCUMFERENCE
Penis length is not the only factor in determining penis size. The width, girth, or fatness, of a penis are also important aspects when considering how you measure up.
Most people have a penis that is either longer and thinner, or shorter and fatter. To compare how the girth of your penis compares to the population, use the following instructions to determine your penile circumference (distance around the widest part of your penis).
1. Stimulate yourself into an erectile state.
2. Place the fabric ruler or string end on the widest part of your penis and wrap it once around carefully. Mark the spot where the string first touches itself.
3. If using string, take the marked string and lay it against the ruler. Read to the nearest quarter-inch measurement.
4. Record this number on a piece of paper.
5. Repeat this measurement two more times, preferably with different erections and preferably on different days as penis size will differ depending on the level of arousal, time of day, room temperature, and recent sexual activity.