Breast Flange Sizing: A New Mom’s Guide

Breast Flange Sizing: A New Mom’s Guide

If you’re a new mother, you may feel overwhelmed by all the different lifestyle changes happening to you. When it comes to breastfeeding, it’s important to know some helpful tips and tricks to make life easier for you and your little one. Many don’t know that it’s essential to find a breast pump that will fit you well. 

As we all know, breasts come in different sizes and shapes, so it’s important to know what best size breast pump flange you need. 

Having the wrong size can impact your breast milk supply, or worse, lead to sore and irritated nipples or clogged milk ducts. If you’re having trouble breastfeeding, it may be due to having the wrong size breast flange. 

Keep reading to learn about Greater Than's guide to helping you understand the size you need for your breast pump flange!  

What Are Breast Pump Flanges? 

A breast pump flange, also typically known as a breast shield, is the part of the breast pump that comes into contact with your body when placed onto your breast and nipple. It’s the plastic piece that directly fits over your nipple to form a seal around your areola. 

Flanges are shaped like a funnel, so it forms a vacuum seal by drawing your nipple into the tunnel of the pump and forming a vacuum seal over your areola. This creates the necessary suction to help extract your breast milk. 

They can come in a wide range of hard plastic, silicone, or even glass. It all depends on you and what you find comfortable! Flanges are also available in various sizes, which can make it overwhelming to find the perfect one. 

Knowing how to find the size that fits you best can help you avoid a lot of trial and error.

How Do You Know Which Breast Flange Fits You Best? 

This process may take time, depending on finding the perfect size and material that works best for you. It usually does require some trial and error, but knowing how to measure it can help make the process shorter. 

The first step is to find out if your preferred breast pump has a measuring guide to go along with it. Brands can have their own specific guides, and while this can be helpful, it can still be beneficial to know how to measure on your own. 

How To Measure To Find Your Flange Size

The first step is to find a measuring tape around your house. Once you have that, you then measure the diameter of your nipple. This means using measurement in millimeters and going across the base of your nipple. 

The standard flange size is around 24 millimeters, but depending on your nipple size, you may need a smaller or larger size. 

Here are some things to remember while you’re measuring: 

  • Flange measurement is based on the diameter of your nipple when it meets your areola, so make sure to be careful and not include measuring your areola. You could end up with a flange that is too wide. 
  • Be careful not to measure the nipple at the top instead of the base. You could end up with a measurement too small, which means your flange could be too tight. 
  • Always make sure to measure both nipples in case you need two different sizes. 

How Do You Know When Your Flange Does Not Fit Correctly? 

The best way to know when your breast flange fits correctly is when you place it on your breast. Here are two questions to keep in mind when you’re testing out what size works best for you:

  • Are you experiencing nipple discomfort during or after the session? 
  • Are your nipples becoming discolored, chapped, or injured during or after a nursing session? 

If you answered yes to these, you immediately know that the flange size is not right. When you put the breast shield on, it should suction your breast and mimic how your baby would suck.

If your nipple is not being suctioned gently, it’s going to be injured by friction, which will only get worse each time you pump. If you’re wondering what it should feel like when you have the right size flange, here is what you should feel and keep in mind when trying out a breast pump:

  • Your nipple is moving freely in and out of the tunnel. You do not feel any friction, swelling, or see redness. If you do, your flange could be too small in size.
  • Your breast movement mimics gentle sucking when you turn the suction on the flange on. It should not be too rough or feel like it’s not moving enough. 
  • Your nipple can move freely in the funnel of the flange. Only a little amount of your areola is pulled into the tunnel. Too little movement can indicate your flange is too small, while too much movement shows your flange is too big. 

Your breast flange size can change shape, so it’s important to regularly measure and check your flange fit, especially if you feel any discomfort while pumping. 

Having the Right Breast Flange Size is Important


At Greater Than, we know how much of a whirlwind it is when you become a new mother. There’s a lot to keep in mind to take care of yourself and your little one. If you’re worried that your breast milk supply is low or you’re having trouble with pumping after a session, it could be related to whether your flange fits correctly. 

Having the right size flange is essential for maintaining your comfort while breastfeeding. It can be helpful to check if it fits right before turning the pump on. This can prevent chafing or rubbing, making your nipple swell and possibly change shape.  

If you’re worried that your breast milk supply is low from something other than an incorrect nipple flange, make sure you’re hydrating and eating well. It’s normal to be anxious about whether or not your breastmilk supply is enough, and if your baby is growing, then chances are they are healthy. 

At Greater Than, we care about moms. We want you to have the information you need in order to take care of yourself and your little one and, hopefully, make your life a little easier.  If you have any questions or concerns about your breast milk supply, always make sure to reach out to your healthcare provider and schedule a physical exam if needed. 


Breastfeeding | World Health Organization 

Nipple Shields | La Leche League GB 

Changes of Your Nipple and Areola | Verywell Health

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