Menstrual Cup Sizing Tips That Don’t Fit on the Box

Whether you’re shopping for a menstrual cup on the shelves at the local co-op, or getting lost in an hours-long internet haze of cup reviews, it’s hard to know definitively whether or not a particular cup size is going to be right for you. As sellers and manufacturers of menstrual cups, it’s therefore impossible to tell someone definitively, “Yes! This size will definitely work!” — the folks at Gap have it easier in that respect, with measurable waist sizes, and fitting rooms in order to try before you buy. So without fitting rooms for menstrual cup shoppers, how do you decide which size to buy?

A person holds three menstrual cups like a bouquet.

How Cup Sizes Work

Sizing has traditionally had two parameters: 1) your age and 2) whether or not you’ve vaginally given birth. With the first modern menstrual cups, it has been suggested that those under 35 who haven’t given birth vaginally should go for the smaller option, while those over 35 or who have given birth should go for the larger option. This isn’t necessarily bad information to go off of, but it is a little over-simplistic. There’s a third parameter that is really useful in helping find the right cup size, 3) your cervix height. Some teens have a high cervix, and some people over 35 have a low cervix. Knowing approximately where the cervix resides for you during menstruation can help you know what size and length cup might suit you best. We always recommend checking during shark week (ie. when you’ll need your menstrual cup!) since the cervix tends to shift positions at that time of the month. 

How to check your cervix height? Insert your finger until you feel your cervix (it will feel a lot like the tip of your nose). Then see how many knuckles deep it is, and use a centimeter ruler against your finger to measure to the knuckle for a more precise measurement. Check out this throwback GladRags video for more tips about finding your cervix.

There are a few other considerations that could affect your cup decision. Athletics, pelvic floor health, light stress incontinence, and bladder sensitivity are a few. This comes more into play when considering cup shape and stiffness, but you might go against sizing suggestions if you’re a barre class regular or can feel any internal period protection against your bladder — the smaller size could be better held into place by toned muscles as well as keep from feeling internal pressure. Similarly, softer pelvic floor toning and light stress incontinence might find the larger size stays in place best.

For those with a serious heavy flow and a lifestyle that prevents changing a smaller cup more frequently, a few extra milliliters of cup capacity might tip you over towards the larger size. Luckily, for those with a light to regular flow, any size will work, so long as you always take out and wash that cup once every 12 hours. 

One final consideration in figuring out your ideal size is to look out for companies who have an “exchange program” (in quotes because you should never actually send a company your used menstrual cup) or money-back guarantee. At, you can try another size XO Flo menstrual cup if the one you bought wasn’t the right fit. I personally recommend giving a menstrual cup a try even if you’re not sure which one might be right for you — even if it’s not the perfect cup on day 1, you’ll know which features or shape or length or stiffness aren’t characteristics you want in your next cup. (And, as always, I’ll remind you to not try out a cup for the very first time on a high stakes day such as your cousin’s outdoor wedding.)

Two sizes of XO Flo menstrual cups sit on a bathroom counter.

If you have any questions about your particular situation, the GladRags customer service team is happy to help! Just remember that until we have space-age OBGYN technology to accurately size the vaginal canal for menstrual cup shopping, the best way to find the best cup for you is to get to know your body, chat with educated and informed menstrual cup experts, and give one a try.

A person playfully looks through two different sized menstrual cups.