Flange Sizing Guide for Pumping Moms

breastfeeding pumping Feb 16, 2023
A baby bottle filled with breastmilk next to a manual breast pump.

Did you know that most breast pumps come with flanges that are too big?

Yeah, me neither.

Unfortunately, I learned this lesson the hard (and painful) way.

Let’s walk through the basics of the flange, what it’s used for and how to ensure a proper fit.



What is the flange of a breastpump?

The flange, also called a breast shield, is the cone-shaped funnel that fits over the nipple, areola and breast. It forms a seal around the areola to produce suction on the nipple.



What are the risks of using the wrong size flange?

There are several risks that can happen if you are using a flange that is either too big or too small.

  1. Pain or discomfort during use.
  2. Chafing.
  3. Nipple damage that continues to get worse.
  4. Rashes.
  5. Decreased milk output.


How to know if your flange is the right size.

There are a few ways to make sure you get the right fit. 

  • Make sure you are measuring in millimeters.
  • Measure just the base of the nipple.
  • Use a nipple sizer.
  • Use a caliper.

Ask for help when you measure because it can be really awkward and hard to see the measurement on yourself.

Some pumps will instruct you to add anywhere from 1-5 mm on top of that measurement while others may say to start with the exact size of your nipple.

I suggest buying your size and then one size larger. 

Use the one that feels the most comfortable!

Remember that the goal is to have none of the areola get pulled in when you pump and only the nipple is moving.

You may even find that your nipples are two different sizes and you may need separate sizes of flanges.

If you have larger flanges, you can buy inserts to place inside to make them smaller and more comfortable.

Pro tip: using lubrication like coconut oil can help with comfort as well.



What should it look like when you are pumping?

When using the breast pump, pay close attention to what is being pulled in the flange. Only the nipple should move. The areola should not be pulled in.

Make sure to watch the nipple as it moves.

Trust me, you don’t want it rubbing up against the side each time it is pulled in. If it is rubbing, size up.

Large gaps between the nipple and the wall or pulling the areola means your flange is too large and it is time to size down.

You shouldn’t feel any discomfort. It should feel like a gentle pull on the nipple.



What if they don’t offer a flange in my size?

When searching for a flange in your size, first start with the manufacturer’s website. They will have all their product information available. 

If the manufacturer does not have the size you need, you may be able to find some third-party sellers of pump parts on Amazon. I personally used Maymom for my Spectra and they worked out great.

You can also look into getting cushion inserts. Companies like Medela, BeauGen and Pumpin Pal sell products that might help.

Take time, do your research, read reviews, and make the decision that is best for you.


Here is my plea: seek out help if you cannot find the right flange size. Motherhood is hard, but pumping shouldn't be a source of stress.

It shouldn’t be painful when using a breast pump - if you are having pain, GET HELP!

>>> Looking for evidence-based information on combining formula and breastmilk? The Simple Guide to Combination Feeding can help you feel confident with feeding your baby from birth to their first birthday - wherever your feeding journey takes you. <<<


Want to put your breastfeeding woes behind you? I am available for 1:1 consultations to help find the best way to feed your baby.

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