Breast Pump Flange Sizing Guide

Using the correct size breast pump flange (aka breast shield) can be very important.  Mums who express often complain of discomfort with expressing and/or low output.  Over the years I have realised that finding the correct size flange can help decrease this discomfort and potentially increase output. 


Here is an article I wrote about why it is so important, plus more information on sizing


There are 3 elements to flange sizing:

1. The size of your nipple

2. How the flange feels when you are pumping

3. How your body responds to it

Up until August 2020 I was following the advice of 'measure the diameter and add 4mm', and that was the end of the story....


Then I started allowing customers to test out flanges in person.  I quickly realised that the majority of people preferred a size that was very close to the actual diameter of their nipple.  But there are also some who prefer a size bigger, some even a size smaller.  Some also seem to have a 'magic spot' - a place where more milk flows even if the flange seems a little uncomfortable.  And sometimes people test out different sizes, buy one, realise that it is not quite right, and need to try others again - ie it may take some trial and error.

Since August 2020 I have not seen anyone need bigger than a 21mm flange.  If you have been told that you need a flange larger than 21mm I would strongly recommend you double (or triple or even quadruple if needed) check using this information.


If you are in Perth you are welcome to come try out different sizes in person.  If you are interstate, or want to borrow different sizes for a bit longer, I now have a new option - Flange Lending Service - borrow up to 3 different sizes to test out before deciding on a size. Available Australia wide.  Click here for more information

You are welcome to contact me if you have any questions.  You may also send me a video of you using your current flange - please make sure it is from the beginning of the session, preferably so you can see the nipple at rest before you start the pump

Flange Sizing Guide (4).png

NOTE - measuring is just the first step. You may need to try multiple sizes before finding the one that works for you.


Click on the ruler (with the Maymom logo) to download a print at home nipple ruler (ignore that it says to add 2-4mm - I have revised that advice and will be changing the information soon)

nipple ruler1.PNG

I have found the rule of measuring after expressing for 5mins and adding 1-2mm can be inaccurate as the nipple will swell to meet the flange you are currently using, which artificially increases the size (it's like trying on a t-shirt over a jumper - you either wouldn't do it or know that you can go down a few sizes).  Also, the guides that make you cut out holes and place over your nipple may not be completely accurate either.

A note on elastic nipples - I have often had people come to me saying they think they have 'elastic nipples' and do I have a product that will help. Often their nipple is reaching almost the very end of the funnel or may even be hitting it.  Some have heard that Pumpin Pal flanges will help them.  Over time I have realised that a lot of people who think they have elastic nipples are actually using the wrong size, usually much too big.  Before you spend lots of money on other flanges that may be the wrong size, please use this guide to figure out if you are using the right size.

If you are not using the nipple ruler on this page or a caliper please be very careful to read the measurement closely and measure a few mm above the areola - I find a lot of people are measuring themselves too big.


Note that your nipple may get larger over time as it is drawn out from feeding/expressing, or it could decrease as any swelling subsides. 


Personal and professional experience

Maymom® sizing  guide

Medela® breastshield sizing tool -