Diameter

here's a tip:

Take a strip of paper, wrap it around your dick when hard, matching end to end. Mark it with a pencil. Take it off and measure it with a straight ruler, then you'll have the circum.:cool:
 
Usually it's wider than it is deep, though how much difference there is varies. As well, it's very hard to get an accurate measure of diameter with a ruler, because of parallax. The paper strip method for finding circumference gives a more accurate measure of thickness.