Flange Sizing: Your in-depth guide

Written by Angel Yarbor, Edited by Jen Meuller IBCLC, illustrations 
by Natasha Dodge


Flange sizing may seem like a foreign concept when first embarking into the world of bodyfeeding. In fact, you probably never heard of a flange until deciding to pump for your little one, opening your breast pump packaging, finding all of those goodies inside, and asking yourself, “what is this thing?”  

Honestly, we’ve all been there! 

Well, good news, we’re here to help!

First, What is a flange?

A flange is the funnel part of a pump that makes contact with the breast. Having the proper flange tube size can greatly impact how your pumping experience may ensue. Ensuring you have the correct fit is very important. 

You might ask why the fit is so important?

Flanges come in various sizes with tubes ranging from 15 to 36mm and larger,’ however, in most cases, full pump starter kits come with about a size 24mm flange. In all actuality, you may need a smaller or bigger size. And, to make it even more fun, you might need two different-sized flanges - one for each side -  to get the job done!

The flange funnel creates a vacuum seal around the areola and the nipple should move freely within the tube. While every brand of pump offers slightly different sizing, the principles are the same for all of them. The video below has a good illustration of proper and improper fit. 

Below are a few things you might notice regarding ill-fitting flange sizing:

  1. Nipple rubbing against the flange and causing pain

  2. Your areola or additional breast tissue being sucked into the tunnel of the flange

  3. Redness, or discoloration after pumping

  4. Blanching where the flange touches (skin turning lighter or white as blood circulation is restricted); 

  5. That breast/chest still feels like they need to be emptied.

  6. That you are working extremely hard for each ounce.

If any of the above issues are happening to you it could be a sign that you need to revisit your flange size AND speak to an IBCLC. Your IBCLC can help g you figure out where to start when sizing and assess the diameter, length, and elasticity of your nipple. They can also rule out other possible causes of your pump issues and determine if further assistance with them is needed.

Finding the right accessories for nursing and pumping for your baby may take a bit of trial and error before finding your groove. Having an IBCLC on your team can help your journey go a bit smoother!  To book a flange fitting or full consultation with our experienced IBCLCs, call us at 202.293.5182 or your schedule online