If you're new to pumping, you’ve probably already realized—it’s not just about getting a good pump. It’s also about getting the right fit. And that means finding the correct breast pump flange size. Flanges are those funnel-like parts that go over your nipples during pumping. And yes, size matters here. Using the wrong one can lead to poor milk output, pain, or just a frustrating pumping session.

So if pumping has been uncomfortable, or you’re not getting as much milk as expected, your flanges on the breast pump might be the reason. Let’s break it down in the simplest, most real way possible.

What is a breast pump flange?

A breast pump flange, sometimes called a breast shield, is the part that goes over your nipple and areola when you're pumping. It’s what connects your boob to the pump and helps create the suction that pulls milk out. It seems pretty straightforward, right? But here’s the thing—not all nipples are the same size, so the flange size shouldn’t be one-size-fits-all either.

Most pumps come with a “standard” size, usually 24mm, but that doesn’t mean it’ll work for everyone. You might need a smaller or bigger one, depending on your nipple size. And honestly, if the flange doesn’t fit right, it can be super uncomfortable. You could end up with sore nipples, clogged ducts, or just feeling like pumping is not working at all. 

You can measure your nipple diameter using a soft measuring tape or ruler (in mm) and then find a flange just a few millimeters larger. For example, if your nipple is 18mm, a 21mm or 22mm flange might be a good starting point.

If you’ve been pumping for a while and just now realized your breast pump flange might be off, don’t worry. It’s never too late to make a switch. Try a different size and see how your body responds. You might be surprised by how much more comfortable and productive pumping becomes. And don’t be afraid to experiment or reach out for support. Lactation consultants can also help if you are pumping for the first time and need expert guidance on choosing the correct flange size. 

Why is flange size important?

Here’s the truth: the correct flange size can completely change your pumping experience.

When your flange fits properly:

• Pumping feels way more comfortable.

• Milk flows more efficiently.

• You’re less likely to deal with pain, chafing, or irritation.

• You’ll reduce the risk of blocked ducts or engorgement.

• You might even cut down on pumping time.

Conversely, using the wrong flange size can cause issues like nipple pain or swelling, redness or friction rings, and even low milk output (even if your body is making enough). It can also just leave you feeling frustrated, like pumping simply isn’t working the way it should. 

Finding the correct flange size might seem like a small detail, but it can seriously impact your pumping success. And here’s the good news! If you haven’t found the correct flange size yet, you must check our breastfeeding and pumping essentials to help you on your pumping journey.