LENGTH IS KEY
While we are speaking of "size", it's important to clarify that the most important dimension of a cup is its length, not its diameter. Simply enough, a cup should completely fit inside your vagina (except the stem, which can stick out!). If it doesn't, it won't be able to adhere properly and you will experience leaks.
So how do you determine if a cup is too long for you? As we explained in our cup how-to, it's all about your cervix. Our cervix connects our vagina to our uterus, and, like most other things, is unique to each body! In particularly, cervix come in a lot of different heights (from very low to quite high). Your cervix height is the most important thing to consider when choosing a cup :)
HOW TO MEASURE YOUR CERVIX HEIGHT
We know it can seem a bit intimidating, but measuring your cervix is actually super quick & easy and can be done at home. We've seen some blogs suggest women see their doctor for this but, while we always advocate seeking professional advice for any medical issue, this is really not worth the trip to your gyno! Quite on the contrary, we should all feel comfortable enough with our bodies to explore it (safely!) in the comfort of our own homes.
Since periods often affect our bodies physically, we highly suggest doing this while you're menstruating. As always, the first rule is to carefully wash your hands. Then, take your finger and slide it into your vagina (as if you were inserting a tampon). Keep going until you feel something a bit firmer, similar to the touch to the tip of your nose. Good job: that's your cervix!
If you can only get one joint of your finger in then you have a very low cervix. Two joints? You have an average cervix height. If you can fit your entire finger into your vagina before you touch your cervix then you have a high cervix. Generally, a bigger cup size is better for a higher cervix & viceversa.
If you want to be a bit more precise, with the tip of your finger still touching your cervix, place your thumb along your finger to mark all the length that fits inside. Keep the thumb in place as you remove your finger, and measure the distance to the tip of your finger with a ruler. Then you can easily compare that to the length of different cups!
AGE & PREGNANCY
If we go back to our initial diagram, you'll see that a bigger size is recommended for women over 30 or who've given birth. While this is a good general tip, it's definitely not definitive. Some women in their 30s may find that a bigger cup is uncomfortable, while some younger girls may experience leaks with a small size. Because our bodies are all different, we shouldn't follow these tips blindly but rather take the time to understand what they mean.
Cups have to create suction with our vaginal walls, so it's important the cup sits pretty snugly inside you. Generally speaking, giving birth and ageing can both affect the size of our vaginal canal. In birth, this is because muscles tend to loosen in preparation for labor. Because of this, it's also important to note that women who've given birth through C-section may sometimes prefer a larger size too.
In the end, you know your body best! For example, if you're a mother or over 30, but do a lot of exercise (especially of your pelvic muscles) than your vaginal muscles will be tighter & stronger. In this case a smaller size would probably work best for your body!
In general, it's good to remember that our vagina can easily expand but will struggle to constantly hold something in place. So if you're really undecided about which size to choose, sizing up may be more comfortable.
Unlike pads or tampons, your flow doesn't really need to be taken into consideration when choosing a cup. Cups have a much larger capacity: while tampons & pads should be changed every 4-6 hours, cups can usually last you 12 hours (although some women prefer rinsing them out more often).
If you experience very heavy flows, however, then choosing a larger size may be best. However, you should still measure your cervix before making a definitive choice! A cup that's too long won't work - so using a smaller cup & changing it more frequently is definitely best in this case.
Buy your perfect cup here!