Determining Your Correct Flange Size (So Pumping Doesn’t Hurt!)

Guidance on how to determine your best breast pump flange fit.

If breast pumping is painful for you, your breasts are becoming red and tender after pumping, or you are not pumping enough breast milk, you may need to check and see if you are using the correct flange size.  Pumping is not exactly a wonderful experience, but it should never be a painful experience.  Pumping through pain can lead to nipple damage and clogged milk ducts.  It can also result in a drop in milk supply.  Thankfully, there is one change you can make that will almost guarantee a more comfortable pumping experience.

Related article: 10 Reasons for a Sudden Drop in Milk Supply (and What To Do About It!)

Most breast pumps you obtain through insurance only come with 1-2 standard flange sizes.  This is usually a 24mm and a 27/28mm flange.  However, that might not be the correct flange size for your breasts.  You may need a smaller or larger flange depending on the size of your nipple. Using the wrong size flange can result in pain, discomfort, and low milk supply.

Determine Nipple Size to Find Your Correct Flange Size

Did you know that nipples come in all shapes, colors and sizes?  There are four shapes of nipples: normal, flat, inverted, and protruding.

Types of nipples to determine correct flange pump size. | Work Breastfeed Mom

The color of your nipple is usually related to your skin color, but they can also change due to hormone levels.  Raise of hands: how many of you experienced dark nipples in pregnancy? *raises both hands*

Nipples also come in various different sizes, ranging from smaller than a penny to the size of a half dollar.  That’s quite a range! Because of these differences, the standard flange size may not be your standard size.

To add another level of complexity, your nipples can change over time.  Did your areolas increase in size during pregnancy?  Have they expanded since you started breastfeeding?  Are they different during this breastfeeding journey than with your first child?  All of these factors can alter the correct flange size you should use.

Related article: How to Lose Weight While Breastfeeding Without Affecting Milk Supply

Your nipples and areolas are also elastic.  It has been estimated that a woman’s nipple and areola stretch up to 50% of its normal size when using a breast pump.  If you can see that your nipples stretch all the way to the back of the flange whenever you pump and you feel that your areolas are experiencing more trauma than your actual nipple, you probably have elastic nipples.  Feel free to add this to your resume.

Because of all these factors, it is incredibly important that you find your correct flange size.  You will be hooked up to your pump multiple times a day, multiple times a week, for close to a year or more.  You need to ensure that you are protecting and caring for your nipples by understanding breast pump flange fit. Pumping with the wrong size flange can damage your nipples and lead to low milk production. We cover that in our article Does Flange Size Affect Milk Output? Yes, Here’s How.

Related article: Pumping Supplies: All the Essentials You Need (and What You Don’t!)

What Flange Size Do I Need?

  1. Preferably after pumping or breastfeeding your baby, place the edge of a ruler or tape measure at the base of your nipple.  Do not include your areolas (the dark skin around your nipple).  
  2. Measure the width of your nipple in centimeters.
  3. Multiply the measurement by 10 to calculate your nipple size in millimeters.  Ex. 2 cm = 20 mm.
  4. Choose a flange size that is 1-2 mm larger than your nipple.
Medela Flange Size Guide to determine correct breast pump flange size. | Work Breastfeed Mom

Medela Flange Sizes:

Related article: Milk Still Flowing After 30 Minutes of Pumping? It Can Happen.

Spectra Flange Sizes:

What Happens if Flanges are Too Big?

If your flange size is too big, you areola will be pulled into the flange along with your nipple.  This is not what is supposed to happen when you pump breast milk and can lead to nipple injury or blocked milk ducts.  Your nipple should be the only part of your breast inside the breast flange.  Think about the way your baby latches onto your breast.  She takes your nipple and areola into her mouth (similar to the flange resting against your breast), but only the nipple goes into the back of her mouth in order to express milk:

Nipple in baby's mouth to determine correct breast pump flange size. | Work Breastfeed Mom

The flange should comfortably rest against your areola with no space between (similar to baby’s lips).  What should your nipple look like in flange? It should look like this:

Determine Correct Breast Pump Flange Size | Work Breastfeed Mom

If you are still unsure what your correct flange size is or are experiencing continued pain after measuring, try purchasing different sizes until you find one that feels comfortable.  This is the most accurate method of identifying your correct flange size.  Using a ruler should give you an idea of where you fall on the nipple size spectrum.  However, measurements and size guides are no replacement for actually holding a flange up to your breast.  Just like it’s easy to order shoes that don’t fit, it’s easy to order nipple funnels that aren’t quite right!

Related article: The Complete Guide on How to Pump at Work

Keep in mind, too, that you may need to re-measure your nipple every few months to see if and how much your nipple size has changed the longer you breastfeed and/or pump breast milk.  If your nipple size increases/decreases, you may need to switch to a larger/smaller flange size to maintain a comfortable pumping experience. Additionally, if you notice that your flange has cracked or become discolored it may be time to replace it. See our guide on How Often to Replace Pump Parts-Everything You Need to Know for more information.

If you find that no matter what flange size you are using, it’s still uncomfortable to pump you can try adding a bit of coconut oil to the flange to provide some lubrication. Additionally, you can also try BeauGen Cushions. BeauGen Cushions are silicone pads that rest inside of the pump flange. Check out our in depth review BeauGen Cushions: What Exactly Are They? Do I Need Them?

Related article: Baby Refusing Bottle? Try This.

And finally, a friendly reminder that breastfeeding supplies are covered by health savings account or flex spending accounts if you have one through your insurance provider.

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Shannon Tisdale
Shannon founded Work Breastfeed Mom in 2019 during her second round of pumping at work. She was tired of googling the same pumping questions over and over again, and discouraged at the lack of websites aimed at working breastfeeding moms. So, she created one herself. Shannon lives, works, and doles out Puffs to her little people in sunny Florida. She has her MBA and works as a strategic planner for a large healthcare system. She is passionate about coffee, memoirs, paddle boarding, and skincare routines. Shannon is mom to Scarlett and Ivy, and hopes to have more babies if her career allows.