Cup capacity is the one number on your period that is already measured for you — if you know how to read it.
Most period products hide the number you actually want. A pad or tampon absorbs, and unless you weigh it, the volume disappears. A menstrual cup is different: it is a measuring vessel that happens to be a period product.
That makes cups the easiest way to answer a question a lot of people cannot answer — how much do I actually bleed?
Capacity varies a lot by brand and model, so treat these as broad bands rather than exact figures. The reliable number is the one printed on your own cup or in its packaging — most manufacturers state capacity in millilitres, and many mould measurement lines into the cup itself.
| Cup type | Rough capacity range |
|---|---|
| Small / "size A" / low-cervix models | about 15–25 ml |
| Large / "size B" | about 25–35 ml |
| High-capacity models | about 35–40 ml or more |
Two things worth knowing before you compare:
The useful measurement is not your cup's capacity — it is how full it was, and how often you emptied it.
That total is your cycle volume. Doing it by hand for a full period is tedious, which is the entire reason PeriodVol exists — you tap how full the cup was and it does the arithmetic and keeps the running total, on your device, with no account.
If you have read about heavy periods you have probably seen 80 ml mentioned. It is the long-standing clinical marker for heavy menstrual bleeding (HMB) — a total across one whole period, not a single day.
It is worth knowing mainly because it gives you something concrete to bring to a doctor. "My periods feel heavy" is hard to act on. "My last three cycles came out around 95 ml, and I was emptying a 30 ml cup three times on day two" is a different conversation.
The 80 ml threshold is a reference point for that conversation, not a diagnosis. Plenty of people above it are fine, and plenty below it have symptoms worth investigating. Volume is one signal among several — fatigue, clots, flooding, and how much your period disrupts your life all matter, and a clinician weighs them together.
| Cup | Tampon | Pad | |
|---|---|---|---|
| Gives a direct volume | Yes | No | No |
| Capacity stated by maker | Usually, in ml | As absorbency grams | Rarely standardised |
| How you estimate | Read fullness | Estimate saturation | Estimate saturation |
Tampon absorbency at least follows a standard — regular, super and super plus correspond to defined absorbency ranges in grams — so saturation estimates are workable. Pads are the hardest, because "regular" and "overnight" mean whatever each brand decides.
If you want the closest thing to a real measurement without weighing anything, a cup is it.
Most menstrual cups hold roughly 15–40 ml depending on size and model. Small or low-cervix cups are usually around 15–25 ml and larger ones around 25–35 ml, with some high-capacity models above that. Check the figure printed on your own cup, since brands differ.
Not on its own. Heavy menstrual bleeding is assessed on the total across an entire period — around 80 ml is the usual clinical marker — not on one full cup. A single 30 ml cup filled once is well within an ordinary range.
Note how full the cup is each time you empty it, multiply that fraction by the cup's stated capacity, and add up every emptying across the whole period. PeriodVol does this for you: you tap the fullness and it keeps the cycle total.
More directly than pads or tampons, but it is still an estimate. Cups collect fluid rather than absorbing it, so you can see the volume, though judging fullness by eye and the difference between rim capacity and air-hole level both introduce error.
Emptying a cup more often than the manufacturer suggests, or leaking before then, is a pattern worth recording and raising with a doctor. Bring the numbers — cup size, how full, how many times a day — rather than an impression.