Menstrual cup sizing often involves a choice between a smaller and a larger size, but some companies offer additional options. Sizing denotes the volume of blood the cups can hold.

According to a 2021 study, a smaller size cup is best for people under 30 and those who have not been pregnant or given birth.

A menstrual cup is a flexible container made of rubber or silicone. The person menstruating places the cup inside the vagina to collect blood leaving the uterus.

This article discusses menstrual cup sizing, including how it works, how to choose the right size, and how to tell if it fits correctly. It also lists what questions to ask a doctor.

An image of various menstrual cups.Share on Pinterest
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According to research, manufacturers frequently offer two size choices: one smaller and one larger. Brands designate sizes in different ways, such as:

  • small and large
  • B and A
  • models 1 and 2

Other manufacturers may offer one or two additional size selections. One may be smaller than the usual small size, while another may be larger than the usual large size.

It is worth noting that the dimensions of the smaller and larger size are not consistent across brands. Additionally, size does not necessarily indicate the volume of blood a cup holds.

The right size depends on several factors. Aside from volume, it includes the height of the cervix, which is the lowest part of the uterus that attaches to the vagina. The height of the cervix equates to the length of the vagina.

Menstrual cup manufacturers tend to provide consumers with a general guide on how to choose the right size. That said, a person may need to try several sizes of cups from different brands before finding the optimal one for them. It is also always a good idea to ask a doctor for advice in choosing a cup.

Below are some popular brands:

  • Meluna: This brand offers four sizes, ranging from small to extra large. The website provides a size chart to direct people in their selection based on the heaviness of their flow and whether or not they have experienced childbirth.
  • Diva cup: This brand offers three sizes — models 0, 1, and 2. Model 0 is best for first-time users, model 1 is suitable for medium- to heavy-flow days, and model 2 is best for individuals over the age of 35 with wider vaginal canals.
  • Ruby cup: This brand offers small and medium size options. The website provides a quiz that customers can take to determine their size. The appropriate size depends on their age, cervical height, heaviness of menstrual flow, whether they have experienced childbirth, and whether they have experienced sex with vaginal penetration.
  • Lunette: This brand offers size 1 for people with a light flow and size 2 for those with a heavy flow.

Smaller size vs. larger size

The usual small size is best for people younger than age 30 who have not experienced pregnancy and childbirth. In contrast, the usual large size is best for individuals older than age 30 who have had these experiences.

When the smaller-than-usual size is available, it is suitable for teenagers or those who are just starting to menstruate.

Since the larger size can hold more blood volume, a person with very heavy menstrual periods may prefer this option. Also, the larger size is better for people with a higher cervix, while the smaller size is better for those with a lower cervix.

If a cup is too small, a person may experience leaks because it will not form a seal to the vaginal wall. However, it is worth noting that sometimes leaking may result from other factors, such as incorrect placement or spillage from a cup that has filled to capacity.

Conversely, if a cup is too large, it may feel uncomfortable during insertion or removal and potentially cause an injury. People should never try to force a cup during placement.

When judging fit, someone should be aware that firmness can affect comfort. Aside from the incorrect size, discomfort during insertion and removal may stem from a cup that is too firm.

With these factors in mind, if the cup feels comfortable and works without causing leaks, it is likely the right choice.

Importance of the right fit

It is important to have the right fit because an improperly fitting cup can cause issues. A cup that is too small could suction the cervix, which can result in prolapse — or downward displacement — or pain if pulled during removal.

On the other hand, a cup that is too large may obstruct urine flow. It could also make the cup hard to remove, which may also result in displacement.

A person may wish to consider asking the following questions:

  • Which size is best for me?
  • Would a certain shape or style suit me better than other shapes or styles?
  • Would you recommend a certain brand for me?
  • Which firmness is right for my lifestyle?
  • Would a tampon or pad be better to use?
  • Are there any downsides to using a menstrual cup?
  • How should I clean the cup?

Menstrual cup sizing usually involves two sizes — one smaller and one larger — which manufacturers designate in different ways. Some brands provide one or two additional sizes.

The small size is best for people younger than 30 who have not experienced pregnancy and childbirth. The large size is best for those older than 30 who have not had these experiences.

Each manufacturer’s website offers guides and information to help someone choose the right size.