The best menstrual cup for you depends on a handful of personal factors: your age, whether you’ve given birth, how heavy your flow is, and how high or low your cervix sits. No single cup works for everyone, and material or brand name alone won’t tell you much. Here’s how to narrow it down based on your body.
Size Is the Most Important Decision
Most menstrual cup brands offer two sizes, typically labeled small and large. The sizing split is straightforward: a smaller cup generally works best for people under 30 who haven’t been pregnant or given birth vaginally. A larger cup is typically better for those over 30 or anyone who has experienced pregnancy and childbirth.
Why childbirth matters so much comes down to the pelvic floor. Vaginal delivery stretches the muscles and tissues that hold a cup in place. A small cup may not sit securely or seal properly after that change. Age plays a similar role because pelvic floor tone naturally decreases over time, even without pregnancy. A larger diameter cup compensates for this by creating a better seal against the vaginal walls.
That said, these are starting points. If you’re over 30 but have a light flow and haven’t given birth, a small cup may still be the right call. Your flow volume and cervix height matter just as much as age.
How to Find Your Cervix Height
Cervix height is the factor most people overlook, and it’s the one most likely to make a cup uncomfortable if you get it wrong. Your cervix is the firm, rounded tissue at the top of your vaginal canal. During your period, it often sits lower than usual.
To check, insert a clean finger into your vagina during your period. If you can feel your cervix at or before your first knuckle, you have a low cervix. If you reach past your second knuckle before touching it, your cervix is high. Somewhere in between is average. A low cervix needs a shorter cup body, or the stem will poke out and cause irritation. A high cervix pairs well with a longer cup or one with a longer stem for easier removal.
Flow Volume and Capacity
Menstrual cups hold significantly more fluid than tampons, and you can wear one for up to 12 hours before emptying it. But if your flow is heavy, capacity differences between cups start to matter. Small cups typically hold around 20 to 25 milliliters, while large cups hold 25 to 35 milliliters. Some high-capacity designs go even higher.
If you regularly soak through a super tampon in under two hours, look for a cup on the larger end of the capacity range. If your flow is light to moderate, a standard small cup will likely get you through a full workday or night of sleep without issues.
Firmness: Soft, Medium, or Firm
Cup firmness affects two things: how easily the cup pops open after insertion, and how much you feel it once it’s in place. A firmer cup snaps open more reliably and tends to seal well, which makes it a good choice for beginners or people with strong pelvic floor muscles (runners, dancers, anyone who does a lot of core work). The tradeoff is that some people feel more pressure on the bladder with a firm cup.
A softer cup is more comfortable for people with bladder sensitivity or those who find firm cups create a sense of pressure. The downside is that soft cups can be trickier to open fully inside the vaginal canal, which takes some practice. Interestingly, research comparing cups across brands found that firmness doesn’t correlate with the cup’s material or shape. You can’t predict how firm a cup will be just by looking at it or knowing what it’s made from, so check the manufacturer’s firmness rating or look for user reviews that describe the feel.
Material Differences
Menstrual cups are made from medical-grade silicone, thermoplastic elastomer (TPE), or natural rubber. Silicone is by far the most common and is hypoallergenic, making it safe for people with latex sensitivities. TPE cups are also latex-free and tend to be slightly less expensive. Natural rubber cups work well but are not an option if you have a latex allergy.
All three materials are durable. A well-maintained silicone or TPE cup can last up to 10 years, which is a major reason people switch from disposable products. Between uses, rinsing with water is sufficient during your cycle. Between cycles, boiling the cup for a few minutes sterilizes it for storage.
Choosing a Cup if You Have an IUD
You can use a menstrual cup with an IUD, but the combination does carry a higher risk of IUD displacement. One study found IUD expulsion rates of 5.9% among menstrual cup users compared to 0.5% among non-users. That’s a meaningful difference.
The suspected mechanism is suction. When you pull a sealed cup out without first breaking the seal, negative pressure could tug on the IUD strings. Breaking the suction before removal (by pinching the base of the cup or pressing a finger along the side) is standard advice, though research hasn’t yet confirmed that this technique alone eliminates the risk. If you use an IUD and want to try a cup, it’s worth checking your IUD strings regularly to make sure the device is still in position.
Tips for First-Time Users
If you’ve never used a menstrual cup, a few practical details make the learning curve shorter. Most people need two or three cycles to feel fully comfortable with insertion and removal. During that adjustment period, wearing a panty liner as backup helps with confidence.
Folding technique matters more than most beginners realize. The “C-fold” (folding the cup in half) is the simplest, but it creates the widest insertion point. The “punch-down fold” (pushing one side of the rim down into the cup body) makes the tip narrower and easier to insert, which is especially helpful for teens or anyone new to internal menstrual products. For younger users or those who haven’t had vaginal penetration, starting with the smallest available size and a softer firmness tends to be most comfortable.
Water-based lubricant on the rim of the cup can make insertion smoother. Once the cup is inside, run a finger around the base to make sure it has fully opened and formed a seal. If you feel a dent in the cup wall, it hasn’t opened completely, and rotating it gently or reinserting usually fixes it.
A Quick Sizing Decision Framework
- Under 30, no childbirth, light to moderate flow: Start with a small cup in medium firmness.
- Over 30 or after vaginal delivery: Start with a large cup. Choose firmer if you want an easy-to-open cup, softer if you’re sensitive to pressure.
- Low cervix: Look specifically for short-body cups. Standard-length cups will sit too low and the stem will protrude.
- High cervix: A longer cup or one with an extended stem makes removal easier.
- Very heavy flow: Prioritize capacity over size label. Some “small” high-capacity cups hold more than a standard “large.”
- Active lifestyle or strong pelvic floor: A firmer cup holds its seal better during exercise.
Getting the right cup often takes one round of trial and error. Many brands offer sizing kits with two sizes, and some have return or exchange policies if the first cup doesn’t work. Starting with the guidelines above gets most people to a good fit on the first or second try.