A woman's cervix is approximately 4 cm (about 1.6 inches) long with a diameter of around 3 cm (about 1.2 inches). The cervix is the narrow passage between the uterus and the vagina and is cylindrical in shape. Its size can vary depending on factors such as age, childbirth history (larger in women who have given birth), and reproductive status.

The cervix is located inside the vaginal canal, which averages about 3 to 4 inches deep when unaroused, but this varies individually. A "low cervix" is one that is located less than 3 inches deep inside the vagina, whereas some women have a cervix that is 4 to 5 inches deep or higher.

In summary:

• Cervix length: about 4 cm (1.6 inches)
• Cervix diameter: about 3 cm (1.2 inches)
• Depth position inside the vagina: ranges from less than 3 inches (low cervix) to 4-5 inches or more (high cervix)

These measurements describe the cervix itself, not the entire vaginal canal, which is deeper and flexible. The cervix sits at the upper end of the vaginal canal.