How many period panties do you need?

Period pants are pretty freakin awesome. They're comfy, easy and much better for the environment than tampons and pads. But deciding what absobency and how many pairs you'll need for a happy period isn't so clear. So, read this article to help you work it all out...
How many period panties do your need? WeAreBodyBeautiful explains how to work it out.
By Laura Gladman
April 23, 2020

This isn’t something you can just wing. It’s important to match the panties you buy to your flow, so they’re comfortable and effective throughout your period. But working out how many period panties do you need isn’t so easy.

So, in this article I’ll share some important tips with you and a way to work it out based on my trial of Thinx, Modibodi and Tulip period panties. First, we’ll look at how you’ll wear your pants, then measuring your own flow, matching the pants to your flow, deciding how many pairs you’ll need, and finally testing them out.

How will you wear them?

First, decide how you want to use your period pants.

Period pants work with or without tampons and menstrual cups. find out how's best for you.
Wear period panties alone, as back-up or mix it up!

#1 You can wear period pants as a back-up to a menstrual cup or tampons. If you often suffer leaks or overflow, period pants are an excellent solution for extra protection and reassurance. You’ll need between 1 and 2 pairs per day, for day and night.

#2 You can wear your period pants alone. You can reduce your waste from tampons or pads by switching to period pants. You must match the pants to your flow so you know how long you can wear each pair without leaks or discomfort. Then, check this fits with your lifestyle and daily routine. Depending on how heavy your flow is, you’ll need between 1 to 3 pairs per day. Consider wearing as a back-up if you need more than 3 pairs.

#3 Or you could always try a combination of the above. I like to mix it up and wear a pair of pants when I’m due on. This catches the start of my period so there’s no rush or stress to fit my cup. They’re also brilliant during my latter days where the cup feels like overkill.

We’ll look at both options later. Next, how to measure your own flow.

Know thy flow

To work out your flow, write down:

  1. How many days your period usually lasts
  2. For each day, note if you feel your flow is heavy, moderate or light. Don’t worry how this compares to other people, it’s all about you!
  3. Then, how many period products do you use on each day and how much blood do they each absorb/hold? You’ll usually find the absorbency on the packaging in either grams or millilitres

TIP: It’s best to work in millilitres (as we’ll find out later). To convert grams to millilitres, assume one millilitre of blood weighs approximately 1 gram (it’s precisely 1.06 grams). So, if the absorbency is 9 grams it converts to slightly less than 9 millilitres.

Here’s my flow as an example, first for tampons and then my menstrual cup:

Day Flow # of Tampons & flow
1 Heavy X4 super tampons @ 9 to 12g each = 36 to 48g
2 Heavy X4 super tampons @ 9 to 12g each = 36 to 48g
3 Moderate X3 super tampons @ 9 to 12g each = 27 to 36g
4 Light X3 regular tampons @ 6 to 9g each = 18 to 27g
5 Light X3 regular tampons @ 6 to 9g each = 18 to 27g
(but lots lighter than this)

I find it difficult to manage my flow with tampons. I expect overflow at some point on day 1 & 2 because my flow is inconsistant. And I always leak during a night’s sleep with my heavy flow. Therefore, I switched to a menstrual cup because it holds more fluid. And I love it.

Mooncup menstrual cup has millilitre measurement lines on the cup!
Millilitres gauge lines on the walls of the menstrual cup

It’s easier to measure my flow with my menstrual cup because it has a gauge on the side in millilitres. Although the cup can hold up to 29ml (yikes!), I empty my cup every 8 hours or so (as recommended) and it’s never this full.

Day Flow # menstrual cups & flow
1 Heavy X3 cups @ around 15ml each = 45ml
2 Heavy X3 cups @ around 15ml each = 45ml
3 Moderate X3 cups @ around 10ml each = 30ml
4 Light X3 cups = around 15ml total
5 Light X3 cups = less than 15ml total

Once you have this information you can then decide how many pairs of period panties you’ll need.

Match to your flow

If wearing the pants alone, the aim is to stay protected whilst wearing as few pairs as possible during 24 hours. That’s because you must rinse them after use, so changing them is a bit of a faff especially if you’re at work or out from home.

the fewer period pants you need to match your flow the better!
You need as few pairs as possible, between 1 to 3 per day, depending on your flow.

Tulip advise most people need 2 or 3 pairs per day. Modibodi say it’s common and convenient to change them every 8 to 12 hours. So, this gives you adequate protection overnight through an 8-hour sleep.

Both Thinx and Modibodi say you can wear one pair for 24 hours (if it matches your flow). I’m ok with this if as a back-up to tampons or a cup. That’s because you’ll stay relatively clean and dry throughout. But the idea doesn’t appeal to me when free bleeding into a pair on my heaviest days. You may feel different though, and that’s ok!

Now, different brands have different absorbency pants you can choose. They state the equivalent absorbency in different ways from number of pads, tampons, menstrual cups, millilitres, and even teaspoons! However, it’s tricky to compare pants brands by menstrual product absorbency because these absorbencies aren’t consistent.

For example, Thinx say one tampon absorbs 9ml of blood, Modibodi say it’s 5ml, and Tulip say 7.5ml. Wow! That’s quite a difference.  Therefore, it’s best to compare in millilitres.

Here’s a comparison table of the test brands and the absorbencies you can choose:

Absorbency name # of tampons Absorbency in millilitres
Super light ½ tampon 2.5ml
Light/Moderate 2 tampons 10ml
Moderate/Heavy 2 to 3 tampons 15ml
Heavy/Overnight 3 to 4 tampons 20ml
Lightest days ½ tampon 4.5ml
Light days 1 tampon 9ml
Moderate days 2 tampons 18ml
Heavy days 3 tampons 27ml
Super days 4 tampons 36ml
Tulip panties
One absorbency 2 tampons 15ml

Thinx one tampon = 9ml, Modibodi one tampon = 5ml, Tulip one tampon = 7.5ml

Wearing pants alone

So, using the table above based on wearing pants alone for one day of my heavy flow (45ml):

  • In Tulip panties I need x3 pairs per day
  • For Thinx, a choice of either x2 heavy or super days pants, or x3 moderate days pants
  • And I need x3 moderate/heavy or x3 heavy/overnight Modibodi pants

For my lighter flow days, the same options work but I can wear just one or two pairs per day. This keeps it simple, and most flexible vs buying less absorbent pants for these lighter days.

Note: If my period was any heavier, I don’t think Tulip would suit for me if wearing them alone. But both Thinx and Modibodi can accommodate heavier periods with 3 pairs of pants per day. Modibodi is up to 60ml and Thinx up to around 100ml of flow.

Wearing as a back-up

And if wearing pants as a back-up to tampons or a cup, I’d choose from the same absorbencies as above. That’s because I know they can handle my heavy flow for several hours if I leak or overflow. However, I’d wear just a single pair every 24 hours, or 1 pair during the day changing into a clean pair at night (depending on your preference).

  • In Tulip, Thinx and Modibodi I need 1 or 2 pairs per day of the above absorbencies is wearing as a back-up

So, now match your heaviest flow to the pants absorbencies in the table above. Try to match to 1 to 3 pairs per day, depending on how long you can wear them with your flow.

Next, how many pairs you should buy in total.

How many pairs?

Once you know how many pairs you need for your heaviest days, you must then decide how many pairs you need overall. You can buy enough pairs for each day of your period. Or, to save money, you can wash-&-wear the pants during your period. If you do the latter, you must work out when you can wash and dry them so they’re ready for the next day’s wear.

My preference is to wear the pants primarily as a back-up, but alone on day 4 and 5, so I did it like this:

Day # Tulip Thinx Modibodi
1 with cup 1 pair 1 pair 1 pair
2 with cup 1 pair 1 pair 1 pair
3 with cup 1 pair 1 pair 1 pair
4 alone 1 or 2 pair 1 or 2 pair 1 or 2 pair
5 alone 1 or 2 pair 1 or 2 pair 1 or 2 pair
Total 5 to 7 pair 5 to 7 pair 5 to 7 pair

Note: I prefer at least 2 pairs per day when wearing alone.

Therefore, if wearing them as a back-up over 3 days and alone on 4 and 5 I’d buy:

  • 5 pairs to wash and wear
  • 7 pairs for every day

Also, here’s the breakdown if wearing the pants alone over my 5-day period:

Day # Tulip Thinx Modibodi
1 alone 3 pair 2 or 3 pair 3 pair
2 alone 3 pair 2 or 3 pair 3 pair
3 alone 2 pair 1 or 2 pair 2 pair
4 alone 1 or 2 pair 1 or 2 pair 1 or 2 pair
5 alone 1 or 2 pair 1 or 2 pair 1 or 2 pair
Total 10 to 12 pair 7 to 12 pair 10 to 12 pair

So, if wearing them alone over my 5-day period I’d buy:

  • 5 or 7 pairs to wash and wear
  • 10 or 12 pair for every day

TIP: Another alternative is to buy just enough pairs to test against your heaviest flow. If you’ve got it right and you like them, you can then buy more!

Test them!

And finally, it’s very important to test the pants against your flow, especially if you’re wearing them alone!

Ideally, do this at home. You can monitor how the pants are doing on trips to the loo. See if you can wear them for as long as you expect without feeling damp, or experiencing leaks or smells. Test they work all through the night too. If not, you may need a higher absorbency pair, or to change them more frequently.

However, if you need more than 3 pairs of the highest absorbency in one day, it’s probably best to wear the pants as a back-up.

I hope you find the right pants to give you good protection, so they fit into your day and lifestyle. You can learn more about the quality and wear, fit & comfort, and performance of these brands in this comparison review:

Related: which period pants are best comparison review

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Laura Gladman
I'm a bit obsessed with at-home beauty devices. It's a habit I've had for around 9 years now. I love the science, testing and reviewing them, and sharing my experience and feedback on my site I'm also a crazy dog lady, and I don't care.

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