Fitting Your Breast Shields

Abrie McCoy, CLC
August 20, 2022

Once you have selected the type of pump you plan to use, the next step is to properly fit your breast shield, also referred to as a breast flange.  This 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 to Measure 

To measure, you can use a ruler, downloadable measuring app, electric caliper, or a measuring tool from your pump manufacturer’s website! Some of these tools will measure the width of your nipple using a circular cutout or a linear tool measuring the width from each side of your nipple. Nipples tend to  swell/expand during pumping, so sizing after a few minutes of pumping can help provide a more accurate size!


If using a circular cut out tool, like the one from Pumpables, make sure that the tool itself is not tight on your nipple but also does not have so much space that it draws in your areola.

If measuring your nipple using a ruler or linear measuring tool, you want to measure from the diameter of the base of your nipple , not including the areola. 

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 freely and comfortably within the flange tunnel. 

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!

Sizing Tools:

Willow: Printable Sizing tool & Sizing Guide

Elvie: Elvie Pump Sizing Instructions

Medela: Choosing Your Medela Breast Shield Size

Ameda: Nipple Size Guide

Spectra: Flange Sizing Guide

Momcozy: Breast Shield Sizing Guide Video & Nipple Measuring Guides

Lansinoh: Breast Pump Flange Fit: Sizing Guidance

Motif: Blog: Finding the Right Breast Pump Flange Size & Finding Your Flange Size

Pumpables Tool

Downloadable Measuring Apps:

Ruler, Measuring tape- AR- iOS

Measurement App- Ruler Length- Android