How Big Are Ovaries? Average Size and Common Changes

A healthy adult ovary is roughly the size and shape of an almond, typically measuring about 3 cm long, 2 cm wide, and 1.5 cm thick. In terms of volume, the average premenopausal ovary holds around 5 to 7 mL, but that number shifts considerably over a lifetime, peaking near age 20 and declining steadily through menopause. Those averages also mask real variation from month to month, between left and right sides, and in response to conditions like polycystic ovary syndrome or hormonal contraception.

Average Ovarian Volume Across the Lifespan

Ovarian size is not fixed. A large normative study modeling ovarian volume from childhood through old age found that volume rises from about 0.7 mL at age 2 to a peak of roughly 7.7 mL around age 20, then gradually declines to about 2.8 mL at menopause and continues shrinking after that.¹ Another large study looking at ovarian volumes by decade reported similar trends: about 6.6 mL for women under 30, dropping to around 4.8 mL for women in their 40s, and roughly 2.1 mL for women in their 60s.²

The overall pattern is a long plateau during the reproductive years followed by a sharper drop around menopause. MRI-based research found that maximal ovarian volume stayed relatively stable through the second, third, and early fourth decades of life, hovering between about 7.5 and 9.5 mL, then fell to roughly 4.4 mL by the late 50s. Beyond age 60 in that study, the ovaries were often too small to identify on imaging at all.³

What Happens in Childhood and Puberty

Ovaries are present and growing long before puberty begins. Research in girls between ages 1 and 13 shows that mean ovarian and uterine size is smallest up to about age 8, increases between 9 and 11, and gets noticeably larger after 12, especially once breast development has started.⁴ This growth is continuous throughout childhood rather than happening in a sudden jump.⁵ Even in very young girls, small follicle-like structures can sometimes be spotted on ultrasound, which occasionally alarms parents but is considered normal.

How Ovaries Are Measured

Almost all clinical ovarian measurements come from ultrasound, usually transvaginal in adults. The standard approach treats the ovary as an ellipsoid: the technician measures length, width, and depth, then applies a mathematical formula to estimate volume. A commonly used version is the prolate ellipsoid formula, which multiplies the three diameters and a correction factor.⁶ The resulting number is useful for tracking changes over time, but it is an estimate, not a direct measurement.

One revealing study compared ultrasound-estimated volumes against the actual weight of surgically removed ovaries, taking advantage of the fact that ovarian tissue has a density of about 1.0 g/mL, meaning weight in grams converts directly to volume in milliliters. The ultrasound figures came in at least 27% smaller than the true ovarian volume across all groups studied.⁷ So when you see clinical numbers for “normal ovarian volume,” keep in mind that the real volume is probably somewhat larger. This systematic underestimation matters less for tracking change over time (since the bias is consistent) than for setting absolute cutoffs, such as the volume thresholds used to diagnose polycystic ovary syndrome.

Month-to-Month Shifts During the Menstrual Cycle

Your ovaries do not stay the same size from week to week. During a normal cycle, one ovary develops a dominant follicle that swells to an average diameter of about 21 mm just before ovulation, with a range roughly from 17 to 27 mm.⁸ That fluid-filled follicle adds noticeable volume to the ovary that contains it, which is why the two ovaries may look quite different in size depending on when in your cycle you’re scanned.

After ovulation, the emptied follicle transforms into a corpus luteum, which can itself be a visible cyst-like structure on ultrasound.⁹ If you happen to have an ultrasound during the luteal phase and the radiologist notes a “cyst” on one ovary, it may simply be a normal corpus luteum doing its job. These cyclical structures are the main reason clinicians prefer to schedule baseline pelvic ultrasounds in the early follicular phase, when both ovaries are at their smallest and easiest to assess without the confounding bulk of a mature follicle or corpus luteum.

Are the Right and Left Ovaries the Same Size?

In most people, yes, roughly. A study of women undergoing fertility evaluation found no meaningful difference in volume or follicle count between the right and left ovaries.¹⁰ But this symmetry can break down in certain conditions. In women with PCOS, the right ovary tended to be larger than the left, with average volumes of about 11 mL on the right versus 9 mL on the left, along with a higher follicle count on the right side.¹¹ The reasons for this right-sided bias are not fully understood, though some researchers suspect it relates to differences in blood supply, since the right ovarian artery branches directly off the aorta while the left comes off the renal artery.

A right-sided tendency also shows up in pregnancy. Among women studied in the first trimester, the corpus luteum appeared on the right side in about 54–56% of cases.¹² Whether this reflects a slight right-side dominance in ovulation frequency or some other factor is still debated.

How PCOS Changes Ovarian Size

Polycystic ovary syndrome is the most common condition that pushes ovarian volume above the normal range. On ultrasound, PCOS ovaries appear larger and contain more small follicles than typical ovaries. The traditional diagnostic threshold has been an ovarian volume of 10 mL or greater, along with an elevated follicle count, though recent evidence suggests these cutoffs should be adjusted by age. Research on age-specific thresholds found the best diagnostic accuracy with a 12 mL cutoff for women 24 and under, dropping to 10 mL for ages 25 to 29, and as low as 6 mL for women over 44.¹³ The logic is straightforward: because normal ovarian volume naturally declines with age, so should the bar for calling an ovary “polycystic.”

Polycystic ovary morphology on ultrasound remains one of the recognized diagnostic features of PCOS.¹⁴ But it is worth noting that having polycystic-looking ovaries on a scan does not automatically mean you have PCOS. Many healthy women, especially younger ones, have ovaries that meet the morphology criteria without any symptoms. The diagnosis requires additional features such as irregular periods or signs of excess androgens.

Cysts and Ovarian Enlargement

Beyond PCOS, individual ovarian cysts are the most frequent cause of one ovary looking disproportionately large. Functional cysts, including follicular cysts and corpus luteum cysts, are by far the most common and usually resolve on their own within a cycle or two. But other types persist. Endometriomas (sometimes called “chocolate cysts”) form from endometrial tissue growing on or in the ovary. Dermoid cysts (mature teratomas) are a distinct type containing a grab-bag of tissue types including hair, skin, and sometimes teeth.

All of these can inflate the apparent size of an ovary, and research suggests that larger cysts are associated with reduced markers of ovarian reserve. A study comparing women with different cyst types to healthy controls found that anti-Müllerian hormone (AMH) levels were lowest in the endometrioma group, and that increasing cyst size was independently linked to lower AMH and lower follicle counts even after adjusting for age.¹⁵ Whether the cysts themselves cause the reserve decline or whether both reflect an underlying process is still an active question, but the pattern is clinically relevant for women weighing fertility options.

How Hormonal Contraception Affects Ovarian Size

Combined oral contraceptives suppress the hormonal signals that drive follicle growth each cycle, and the ovaries respond by shrinking. A study comparing ovarian volumes in women on the pill, women using an IUD, and women using no contraception found that the pill group had the smallest ovaries across all phases of the cycle, while the IUD group (whose ovarian hormones are not suppressed by the device) actually had the largest.¹⁶ Some research has described pill-related ovarian shrinkage as reducing volume by roughly half, though the effect appears to reverse within a few months of stopping the pill.

This shrinkage has practical implications for fertility testing. If you are on hormonal contraception and your doctor orders an ultrasound to count your follicles or measure ovarian volume as a gauge of fertility potential, the results will likely understate your actual reserve. For accurate baseline measurements, most fertility specialists ask patients to stop hormonal contraception several months beforehand.

Ovarian Size During Pregnancy and Fertility Treatment

In early pregnancy, the corpus luteum on one ovary persists and produces progesterone to support the pregnancy until the placenta takes over. This corpus luteum averages about 19 mm in diameter during weeks 5 through 9 of pregnancy, then begins to shrink, averaging closer to 17 mm by weeks 10 through 13.¹² An ovary carrying a corpus luteum this size can look conspicuously larger than the other side on a first-trimester ultrasound, which sometimes causes unnecessary worry.

During controlled ovarian stimulation for in-vitro fertilization (IVF), both ovaries are deliberately pushed to grow multiple large follicles simultaneously. It is normal for ovaries to swell considerably during this process, and the enlargement can persist for months during a successful pregnancy.¹⁷ In severe ovarian hyperstimulation syndrome, ovaries that normally measure a few centimeters across can balloon to well over 10 cm, occasionally requiring hospitalization.

The Postmenopausal Shrink

After menopause, the ovaries lose their primary function of cycling through follicle development, and they shrink accordingly. One study found a steep drop in the first year after menopause, from a mean of about 6.3 mL in premenopausal controls down to roughly 2.2 mL, followed by a slower and more gradual decline in subsequent years.¹⁸ Across studies, postmenopausal ovarian volume averages about 2 mL, with the shrinkage becoming more pronounced with each passing decade.²

This shrinkage is part of what makes an unexpectedly large postmenopausal ovary clinically significant. Research has found that postmenopausal women with large ovaries, thickened endometrium, and abnormal bleeding had higher levels of sex steroid hormones and a greater association with endometrial cancer.¹⁹ And even a modestly enlarged postmenopausal ovary, say 2 by 3 cm, has historically prompted further evaluation, sometimes with blood markers like CA-125, to rule out ovarian malignancy.²⁰ What counts as “enlarged” thus depends heavily on age and menopausal status.

When Size Signals an Emergency

Ovarian torsion, where the ovary twists on its blood supply, is one of the few situations where ovarian size becomes an urgent clinical concern. Torsion occurs in roughly 2% to 15% of patients who undergo surgery for an ovarian mass, with the mass itself being the primary risk factor because it gives the ovary enough heft and asymmetry to twist.²¹ But torsion can also happen in normal-sized ovaries, especially in children and adolescents.

In the emergency department, a quick way to assess torsion risk in a patient with acute pelvic pain is by measuring the maximum ovarian diameter on ultrasound. Research found that a 5 cm threshold had strong diagnostic performance in postmenarchal patients, with roughly 91% sensitivity and 92% specificity for torsion, and it could rule out more than 60% of non-torsion cases.²² In practical terms, if an ovary measures under 5 cm in a woman with pelvic pain, torsion is unlikely, which helps guide the decision about whether to go to the operating room.

Does Body Weight or Smoking Change Ovarian Size?

You might expect that body mass index would influence ovarian volume the way it affects many other organ measurements, but the relationship is weak at best. One study of late-reproductive-age women found that ovarian volumes did not differ by body size.²³ Other ovarian reserve markers like AMH and follicle counts showed some variation with BMI in certain analyses, but the physical dimensions of the ovary itself appear largely independent of how much someone weighs.

Smoking is another factor that gets attention for its potential impact on ovarian reserve, but the evidence on actual measurable size changes is surprisingly mixed. A prospective study of women seeking fertility treatment found no significant differences in AMH or total antral follicle count between current smokers, former smokers, and never-smokers.²⁴ A separate analysis found similar results: active smoking was not significantly associated with diminished ovarian reserve based on standard markers, although the authors noted the well-established link between smoking and earlier menopause, suggesting a possible long-term acceleration of ovarian aging that single-timepoint measurements may not capture.²⁵ The upshot: smoking probably does not make your ovaries measurably smaller on any given scan, but the cumulative effect over years could push you toward menopause sooner.

What Happens to Ovarian Size After Surgery

When a cyst is surgically removed from an ovary, the remaining tissue on the operated side tends to be smaller afterward. A study comparing operated and non-operated ovaries in the same patients found that the operated ovary had a significantly lower volume, by roughly 2 mL on average, along with a reduced follicle count. This volume loss was similar regardless of whether the cyst was an endometrioma or a different type.²⁶ Blood flow measurements also showed higher resistance in the operated ovary’s artery, suggesting the tissue’s blood supply was somewhat compromised after surgery.

This is one reason fertility specialists are cautious about recommending cyst removal in women who hope to conceive in the future. Even a skillful excision inevitably removes some healthy ovarian tissue along with the cyst wall. The non-operated ovary typically compensates over time, but the overall egg reserve takes a hit, and for women who are already on the lower end of reserve for their age, that trade-off matters. When a cyst is small, asymptomatic, and does not have worrying features on imaging, a watch-and-wait approach often makes more sense than surgery from a fertility standpoint.