Flange Size Guide

Why is the Right Size So Important?

Who knew that nipple size was such a big deal? The things you learn while pumping! Correctly fitting your breast shields to your nipples is the most important step in comfortably and efficiently emptying your breast—which is the largest contributor to supply. If your breast shields are too small or too large you can damage your breast tissue and you won’t be emptying your breast completely, which will impact your supply. To decide what size works best for you, start by getting an accurate measurement of your nipples.

How To Measure Your Nipples

Think of your nipples as circles­ and you are measuring the diameter. The size of your breast doesn’t matter and neither does your areola (the darker-colored area around the nipple). You are only concerned with the nipple—that protruding bit at the very end of your breast. Sizes range quite a bit and they are ALL normal. It’s even common to have two different-sized nipples, so measure both.

nipple diameter illustration

You can use any ruler from around the house. Convert inches or centimeters to millimeters and use the number in millimeters (mm) to find your breast shield—all breast shields are measured in millimeters.

Once you have sized your nipples, add 2-5mm to determine the size of breast shield that works best for you. Browse our selection of breastshields here

Things to Consider When Picking Your Size(s)

Note that different manufacturers measure their breast shields differently. If you have pumped before, the size you used previously with a different brand is a general indicator of the size you’ll need again but not only can your breasts change with each pregnancy (and during your pumping journey) but each brand of breast pump has slightly different sizing—just like brands of jeans or shoes.

Your correct size might also be different if you are using a high-suction pump, such as the Rumble Tuff, especially with our unique waveform which holds your nipple at the end of the tunnel in the “drop zone”. In general, we suggest using the smaller size in your range.

If you have elastic nipples (your nipples stretch during pumping, hit the back of the tunnel, are painful, and you have trouble emptying your breasts) we recommend the Rumble Tuff Pumpin’ Pals flanges. They are shaped differently and their shape helps keep the tissue back out of the tunnel. Using these in combination with traditional flanges can also elongate the tunnel to keep your nipples from hitting the back.

If you haven’t had your baby yet, note that your breasts will change significantly during pregnancy. You’ll have to wait until you’re breastfeeding to get formally sized but you can measure now—taking note that if your nipples are not somewhere between 20-25mm you might need a size that doesn’t come with most insurance pumps. Depending on your size, it might impact the brand of breast pump that will work for you. Generally, pumps have 2-3 sizes and most do not have more than five sizes.

What Am I Looking For?

  • If you are sized correctly the nipple should move freely in the tunnel. Very, very little of your areola should be in the breast shield.

  • If you see tissue rubbing it can indicate you need a larger size.

  • If your nipple stays in place and you get milk coming back towards you (instead of going into the bottle) it could mean your flange is too large.

  • You should not have red or white rings or patches after pumping and you should not feel discomfort.

  • When finished pumping, your breasts should feel empty and hand expression should confirm this. Measure before pumping. Incorrectly sized flanges will affect the size of your nipples after pumping, and some size increase is also normal while pumping.