Typical ovarian cyst size depends on the type of cyst. In general, ovarian cysts can range from under 0.5 inches (1.27 cm) to more than 12 inches (30.48 cm). The largest type of ovarian cyst is called a cystadenoma. It is benign and fluid-filled, and in rare instances has been found to grow to 40 inches (1.016 m) and weigh more than 100 pounds (45.36 kg).
Ovarian cyst size covers a large range because there are multiple types of ovarian cysts, each with its own characteristics. An ovarian cyst is a small sac filled with fluid that grows within the ovaries in a female body. Many ovarian cysts are non-cancerous, although about 15 percent are malignant. During the childbearing years, it is common for small cysts to form within the ovaries and then spontaneously disintegrate as a part of the menstrual cycle. These are called functional cysts, which tend to go away without intervention.
In addition to functional cysts, there are several types of ovarian cysts that might cause pelvic pain or other symptoms. A follicular cyst is most likely to occur at the time of ovulation and can grow up to 2.3 inches (5.84 cm) in diameter. This type of cyst usually does not create symptoms and might eventually disappear without treatment. A corpus luteum cyst can occur if a follicle does not disintegrate automatically after the release of an egg; instead, the follicle fills with blood and remains on the ovary. This cyst is also unlikely to cause symptoms.
A hemorrhagic cyst is named for the hemorrhage, or bleeding, that occurs within the cyst, leading to abdominal pain. In a dermoid cyst, which usually occurs in young women, the cyst contains body tissues such as fat or hair. This type of ovarian cyst might grow inflamed or become twisted, which causes severe abdominal pain. The average size for dermoid cysts is often between 2 inches (5.08 cm) and 4 inches (10.16 cm), although in some cases they can become as large as 6 inches (15.24 cm).
Endometrial cysts happen in individuals with endometriosis, a chronic condition in which tissue covering the uterus is also found in other areas, such as on the ovaries. The size for a blood-filled endometrial cyst can range from 0.75 inches (1.9 cm) to 8 inches (20.32 cm). Another fluid-filled benign tumor called a cystadenoma can sometimes grow extremely large, up to 12 inches (30.48 cm) or more. In cystadenoma cases, the ovarian cyst size might depend on how the tumor is classified. A serous cystadenoma, containing a watery fluid, will tend to be 2-6 inches (5.08-15.24 cm) in diameter; a mucinous cystadenoma, which is filled with a sticky, thick fluid, is more likely to be 6-12 inches (15.24-30.48 cm) or larger.