Breast Flange/Shield Sizing

Abrie McCoy
November 16, 2022
Choosing a Flange Size

Once you have selected the type of pump you plan to use, the next step is to determine your flange size!

The breast shield, also known as the flange, is the plastic part of the pump that fits over the nipple to create the seal and vacuum. Getting the right fit for a flange is very important for a comfortable pumping experience. Additionally, a flange that is too large or too small can impact milk output as well as the quantity of milk you produced over time. Don’t be afraid to ask for help fitting a breast shield! It can be hard to get it right,  your nipple size can vary from side to side, and your size can even change as you move through your pumping  journey.


How Pumping Works

If you read our milk production blog, you know that your body creates more milk when milk is removed. Resulting in an increase of the hormone Prolactin. This hormone is responsible for your milk production. The hormone responsible for your milk being released (through this super cool thing called the milk ejection reflex or MER) is Oxytocin! The way this hormone is produced in breastfeeding is nipple stimulation. This happens when your baby is on the breast and the movement from their jaw, tongue, and palate makes contact and massages your nipple. While pumping, the flange and pump motor act to mimic nursing.

Importance of Flange Sizing

Previously flange sizing recommendations were to go larger than your nipple size. However, if you were to use a size too large, there is no contact with your nipple! Therefore, the amount of oxytocin is decreased! Which can affect the amount of milk you express and the amount of time it takes to express. Making it especially important to have the right size for you!


How to Measure 

To measure, you simply use a ruler to measure the width of your nipple at the tip. Do not include your areola in this measurement. It is important that you are only accounting for the actual nipple. You want to take the measurement prior to pumping to get an accurate measurement.


how to measure your nipple for flange sizing - what it looks like


Sizing different nipples
Choosing the Size to Use
This measurement is a great starting point for your breast shield/flange size. Refer to your pump manufacturer to choose the closest size shield/flange available. If that size is not comfortable, you can try the next size up or down to test comfort. Again, the key is COMFORT! It should never be painful or uncomfortable while pumping. Your nipple should move through the flange tunnel comfortably.

Nipple sizes vary from person to person. Nipple sizes are not limited to what sizes are available through pump companies. If you find that you need a smaller size than what your pump manufacturer offers on their website, another option would be to use inserts.  These are typically a soft silicone material and sit inside of the flange to modify the size. 

Just like our breasts, our nipples are not twins-they are sisters.It is completely possible for your nipples to be two different sizes or even change sizes over time! If you start to notice that pumping is getting uncomfortable or your output has changed, try sizing again to see if there has been any changes!


Key takeaways:

  • Comfort and output is key!
  • No one size fits all
  • Each nipple can be a different size
  • Nipple size can change over time
  • Pumping should NOT be painful!!!
  • Personalized support from a lactation professional can be helpful!


Helpful Tips:
  • You can check out Maymom flanges (available at Walmart & Amazon) for a variation in flange sizes!
  • Use coconut or olive oil for lubrication.
  • Do the “milkshake” (literally shaking your breasts) before pumping! This helps fat globules get into milk faster.