Know Your Flow: My Handy Menstrual Product Conversion Chart!

which size menstrual cup

Which size menstrual cup or period pants are right for you?

If you’ve been wanting to get into the world of reusable period products but don’t know where to start then never fear! I’m here to answer all your burning questions about which size menstrual cup is best for you or how many pairs of period pants you actually need.

If you’re a pad or tampon wearer, you’ll know how many products you use in your cycle. How many times you change products each day, how long you can leave things before they start to leak. It’s just practice, and it’s the same with reusable products.

We’re all different with different flows and cycle lengths, so there isn’t a one size fits all equation. But using my conversion cart below you can easily figure out which size menstrual cup to buy or how many period pants you might need!

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How Much Do You Bleed?


According to the NHS website, most menstruators will lose less than 80ml of blood (around 16 teaspoons) during their period.

The average is around 30-40ml (6 to 8 teaspoons).

Heavy menstrual bleeding is defined as losing 80ml or more in each period, having periods that last longer than 7 days, or both.

The easiest way to learn about your flow is to use a menstrual cup. This way you can measure exactly how much you’re bleeding.

Often we change tampons or pads before they’re full so it’s hard to gauge exactly how heavy our flow is.

Period Product Options Ranked by Absorbency:

Measurements are approximate and may vary between brands but I’m referencing Saalt Menstrual Cup and ModiBodi period pants for ease:

  • 1x Pair of Heavy Period Pants = 20ml
  • 1x Regular Menstrual Cup = 30ml
  • 1x Small Menstrual Cup = 25ml
  • 1x Super Tampon = 18ml
  • 1x Super Sanitary Pad = 10ml
  • 1x Regular Tampon = 9ml
  • 1x Regular Sanitary Pad = 5ml
  • 1 x MAXI Pair of Period Pants = 60ml!

    (Modibodi have a pair of MAXI period pants that hold a whopping 50ml and can be worn for up to 24 hours! And Wuka have since launched their pair that hold up to 60ml!)

So if you’re thinking of making the switch, here’s how to work things out.

If you’re on the heavy flow side and tend to go through 3 super tampons in one day; you’d probably only have to empty a regular menstrual cup twice a day. Or you could use 2 pairs of period pants – one for the day and one at night. OR one pair of MAXI period pants for the whole 24 hours.

1 Super Tampon =18ml x 3 = 54ml

If your flow is lighter using 2 regular tampons a day, then you’d only need to empty a cup once every 12 hours. Or you could wear one pair of period pants all day without worry!

1 Regular Tampon = 9ml x 2 = 18ml

Sit down and try to work out your flow. Knowing roughly how heavy your period is will really help you understand which size menstrual cup to buy, or how many pairs of period pants you’d need to start things off.

It’s near impossible to know your true flow unless you use a menstrual cup and get all science-y with those measurements! If you’re changing disposable products before they’re at capacity you may think you’re bleeding more than you actually are which can skew the results.

(Remember: It’s not safe to wear a tampon for more than 8 hours. Even if it’s not full you still need to change. You can however wear a menstrual cup for up to 12 hours!)

How Much Can My Menstrual Cup and Period Pants Hold?

How Many Pairs of Period Pants Do I Need to Buy?

If you’d like to know more about menstrual cups or period pants, take a look at my blogs below for all the useful details:

All Your Menstrual Cup Questions Answered!

Period Pants Review and 4 Big Brand Comparison


which size menstrual cup