How to Tell if Your Breast Pump Flanges Fit

Woman using a breast pump

Photographer's Choice / Getty Images

Table of Contents
View All
Table of Contents

A breast pump can be very useful if you're breastfeeding. The device allows you to express breast milk and store it to ensure your baby is fed when you're apart. When choosing a pump, it's important that the flange (also called a breast shield) fits you properly. A flange that doesn't fit can breast soreness and injury as well as reduce the amount of milk you produce.

The Standard Breast Pump Flange

The breast pump flange is the part that connects your breast to the pump. Milk will travel down the breast shield tunnel to the bottle or another collection device.

It's a good idea to check the fit of the pump flange from time to time. All breast pumps come with at least one average-sized breast pump flange. The average flange is between 24 and 27 millimeters (mm)—which corresponds to the size of your nipple—but not everyone who breastfeeds will fit these sizes.

You can get smaller or larger flanges depending on the material: plastic flanges range from 21 mm to 36 mm and there is a 40 mm glass flange available.

Why Size Matters

Not having the right size breast pump flange can cause problems. For instance, you might not be getting the most amount of breast milk possible which can lead to blocked milk ducts. A poor fit can also cause nipple damage, like rub marks and cuts on the nipple.

Many people notice a difference almost immediately after finding the right sized flange. Using the breast pump is more comfortable and the amount of breast milk that they are able to pump begins to increase.

How to Tell If Yours Is a Good Fit

Nearly every breast pump manufacturer will offer a size guide for breast shields. Make sure you review them before buying a breast pump. The Food and Drug Administration (FDA) recommends researching the manufacturer's flange size options. You should also find out whether you'll be able to order a different size if you discover that you need one.

The size of the flange you need is the size of your nipple. You can measure yours using a ruler or measuring tape. Be sure to measure the diameter of the nipple alone—do not include the areola.

When you get your pump, you can tell that the flange is a proper fit if:

  • You are not experiencing pain in your nipple.
  • Your areola should have little or no tissue inside the tunnel of the breast pump.
  • You do not feel areas of the breast that still have milk inside (which indicates the uneven removal of milk).
  • You do not see a white circle at the base of the nipple, nor should your nipple blanch.
  • Your nipple is centered in the flange and moves freely in the tunnel of the breast pump.

When You Need a Different Size

If you don't have the right size, you will want to see if your breast pump came with other flanges or if you will need to order new flanges.

If you go up in size, you might be restricted from using some of the softer plastic flanges. Some breast pump manufacturers have smaller flanges that can fit inside the average-sized flange.

Most breast pumps only come with a 24 mm size flange and manufacturers often only offer the more common sizes (24 mm to 29 mm). The other sizes might also be available, and they are sometimes sold as part of a set of various sizes.

People with other size needs might have to buy from a source other than the one that produced the pump they use. People are often worried that the new flanges they buy from one manufacturer or company won't fit the pump they have from another. While it can be a bit tedious to "mix and match," most pump and flange combinations will work fine.

Finding Help

A lactation consultant can be of great help if you're not sure what size flange you need, or if you think you might need a different flange. If you do not already have a relationship established with a lactation consultant, there are several places you can look for one.

Start by calling the hospital where you gave birth. It's typical that they will have someone who is registered with the International Board of Lactation Consultant Examiners (IBCLC) that can help you determine the issue with sizing.

You can also try a local store that specializes in breastfeeding products or ask your friends, family members, or parents that are part of your play or daycare group who breastfeed if they have recommendations.

A Word From Verywell

Finding the right flange for your breast pump can make your experience less painful and more productive. It can be frustrating to find the right size for you, but there are resources that can help—and getting the perfect fit will be well worth it.

2 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Becker GE, Smith HA, Cooney F. Methods of milk expression for lactating women. Cochrane Database Syst Rev. 2016;9:CD006170. doi:10.1002/14651858.CD006170.pub5

  2. U.S. Food and Drug Administration. Choosing a Breast Pump.

By Robin Elise Weiss, PhD, MPH
Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor.