Set your ruler against your pubic bone just above the base of the penis, and measure to the tip. Thats how the doctors do it. One-quarter of all penises bend in some direction and some bend downward even when erect. Unless the bend is severe or causes you pain, there is nothing wrong or abnormal about your penis. It should not interfere with sexual intercourse.
Some people report that a downward-bending penis is easier to fellate.
In rare cases a condition called Peyrone's Syndrome can arise from childhood diseases. This condition is caused by scarring on one of the two corpora cavernosa within the penis, stunting its effectiveness during erection and causing the penis to bend almost 90 degrees in that direction. If you feel this may be the case, consult a urologist. Male circumcision is the surgical removal of the foreskin from the penis. When performed in a hospital, it is usually done shortly after birth by a doctor or midwife.