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Flange Size Matters

When it comes to pumping, flange size matters. Many moms who begin to use a breast pump may not be aware that the flanges (the funnels/cups that touch your breast) included with your breast pump may contain multiple sizes. Some moms just grab a flange and start pumping, unknowingly using different sizes. Sizing is important because it can affect the comfort of pumping as well as the efficiency of pumping.

Pumping Should Be Comfortable

When you first begin pumping or breastfeeding, you may experience slight discomfort because the pull-tug on your breast tissue is a new sensation. However, pumping should quickly become comfortable. If you have pain on your nipples or areola due to damage from the baby’s latch, you should quickly make an appointment with your local lactation consultant to help you achieve a comfortable and pain free latch. If you feel you have pain while pumping on your nipples or areola due to friction or swelling, the flange size is probably too small or too big. If you have discomfort in your breast, it may be because the pump is not effectively draining the milk, which may be caused by incorrect flange fit.

Flange Sizing

How do you know what size flange to use? Many breast pump company websites now have downloadable measuring tools you can use to accurately measure your flange size. These are great tools to use to ensure you are using the correct size. It is important to note that you should not measure for flange size during pregnancy prior to baby’s birth because the size is likely to change after baby is born. You will also want to be aware that your flange size may change over time and you may have a different flange size for each breast.

A quick and general method to size your flange is to compare your nipple (not including areola) to money (coins). Assess your nipples before you start to pump.

If your nipple is comparable to a dime you will likely fit a 20mm/21mm flange.

If your nipple is comparable to a nickel, you will likely fit a 24mm flange.

If your nipple is comparable to a quarter, you will likely fit a 27mm/28mm flange.

If your nipples are smaller or larger, you can go up or down in size.

While you are pumping, you will want to make sure that your nipple is not rubbing along the inside of the flange. If this is the case, likely you will need to go up in size. Conversely, if a large portion of your areola is being pulled in, which sometimes causes it to swell, you will probably need to go down in size. After you have determined a comfortable fit, you also need to consider if your breasts are being completely drained. If you feel as though you still have milk left in your breasts after pumping (with hands on massage) or you are prone to clogged ducts you may need to change your flange size. If you have sized your flanges correctly and you still feel discomfort a never feel fully drained, you can try several different solutions.

  • Lubricate the inside of your flanges with lanolin, nipple cream, or coconut oil.
  • Use a hands-free pumping bra to ensure adequate seal and suction.
  • While you pump use hands-on active massage.
  • Consider an alternative flange or a flange comfort device.

Ensure you are using adequate suction set to your maximum comfort level and correct pump settings that will initiate your let-down and effectively drain your breast.

If you continue to have pain or have general pumping questions, you can contact your local lactation consultant or breastfeeding support group. Modern Milk offers Mini Lactation Consults where we can address flange fit or pumping pain. You can find more information at

– Katie Kunz, RN, IBCLC


Jennifer, Graves, L., Jacqueline, & Wietzke. (2019, February 20). How to Know If Your Breast Flanges are the Right Size. Retrieved February 18, 2020, from

Medela. (n.d.). Breast Shield Sizing: How to Get the Best Fit. Retrieved February 18, 2020, from