How to Choose the Right Size Breast Flange

Categories: Breastfeeding, Pumping
August 5, 2021

Finding the right size breast flange or shield will help you increase milk output and have the most comfortable pumping sessions possible. Don’t know what size you need? Follow these steps below to find the right size breast flange.

Lansinoh comfort fit flange

Spectra breast pump flange

What is a flange?

A flange, or breast shield, is the cone shaped funnel that fits directly over your nipple, areola, and breast. When using the correct size, it forms a seal between your breast and the plastic or silicone that then creates a vacuum to extract milk.

Why size matters

Using the correct size flange or breast shield will help optimize milk output. If a flange is too small, it could restrict the tissue, potentially causing clogged milk ducts. If the flange is too large, it may not remove all the milk, which could contribute to a lower milk supply. Using an ill-fitting flange can also cause nipple pain or injury.


How to measure your flange size


To determine the best flange size for you, you’ll need to measure your nipple. Take a tape measure or ruler and measure the diameter, or width across, of your nipple in millimeters. Do not include measurements for your areola, the larger part around your nipple. Select your flange size based on your measurement. Common flange sizes relative to nipple measurements are listed below. If your pump manufacturer doesn’t offer one of these sizes, look for the next closest size.

  • If you measure up to 17mm, you’ll fit in a 21mm flange.
  • If you measure up to 20mm, use size 24mm.
  • If you measure up to 23mm, select size 27mm.
  • If you measure up to 26mm, use 30mm.
  • If you measure up to 32mm, use size 36mm.

Flange and breast shield size guide

Keep in mind, breasts are not identical. Each breast may require a different size flange. In fact, your flange size may even change throughout your pumping journey. Before you replace your pump parts, it’s a good idea to remeasure to confirm you are still using the correct size.

Medela tips for proper flange size fit
Image from Medela


The proper fit

You know you have the correct size flange if the following apply:

  • The flange fits comfortably around your breast
  • Only your nipple and a small part or none of your areola enters the tunnel when pumping
  • Your nipple moves freely when pumping without rubbing against the side of the tunnel
  • After pumping, your breasts feel soft and emptied
  • Your milk supply remains the same or improves
  • Overall, your pumping sessions are comfortable and free of pain


A final note

Finding and using the correct size flange is critical to a successful and comfortable pumping experience. If you have questions about the size of your flange or pumping, a lactation consultant can be a great resource. Spending a few minutes determining your flange size will go a long way towards helping you meet and exceed your breastfeeding and pumping goals. Still looking for a breast pump? We can help you get your free breast pump through insurance!