Flange Size Matters

Flange Size Matters

You’ve made the decision to give your baby an incredible gift, your human milk! You’ve done your research, you’ve chosen your breast pump, you open the box, and inside are what looks like two giant cone shaped plastic funnels and you’re not quite sure if these things are truly made for you. Guess what? They’re not. We joke about feeling like cows when we’re pumping, but that’s exactly what the early designers were doing when they made the first flanges. Over the years, manufacturers just never questioned it until moms started taking a stand and fighting back with the help of lactation professionals.

What is a flange & why are there different types?

A flange is a hard plastic funnel type piece that connects to both your breast pump and your collection container that is placed against your breast to facilitate the collection of breastmilk. Flanges come in many shapes, sizes, and materials as indicated below. Just like flange size matters, the shape and material used will matter to you as well.


You might feel more comfortable and more confident using soft silicone flanges instead of hard plastic, using inserts to reduce the tunnel size of your standard flange (more on this later), or removing your standard flange all together and using something like a Pumpin’ Pal flange which can be rotated for comfort and allows you to recline while pumping.

How can I find my size?

The flanges that come with most breast pumps are around a 28mm & 24mm, sometimes larger! Most moms measure between 15mm-21mm though you can find flanges as small as 10mm and as large as 32mm. Here are some simple steps to take when measuring yourself for proper flange fit:

  1. Always measure prior to a pumping or nursing session, when your nipple is in a relaxed state.

  2. Only measure the nipple itself, not including the areola. Updated best practice based on Jeanette Mesite Frem’s FITS method is to measure the tip of the nipple, not the base.

  3. If using a traditional nipple ruler, your nipple should easily fit the hole, not rubbing the sides and not leaving space.

The size you’ve measured is the size you should be using for your flange, however pumping should never be painful and if you find you are able to express milk more effectively and confidently by sizing up or down, please do what is best for you. This is why we recommend having flanges in multiple sizes on hand or a silicone insert kit like the one we offer at Amaris here, which provides you the ability to swap sizes quickly without sacrificing time away from your pump.

How do I know I have the right fit?

First, pumping should never be painful. If you experience pain when pumping, stop and reassess the position of your flange, the size of your flange, and the settings you are using on your pump. It’s important to know that turning your pump to a higher vacuum level will not increase your milk output and can actually damage your breast tissue, cause damage to your nipples or areolas, and just overall make you feel crummy.

When pumping, only your nipple should gently glide inside the tunnel of the flange, not the areola. We don’t want to see any of the areola in the tunnel as this can lead to skin irritation, bleeding, and cracks as well as other complications.

With successful fit, you should see multiple, strong sprays of milk into your collection containers after your letdown occurs. Most pumping parents only need to pump for about 15 minutes or so with the right pump and the right settings, never pumping for more than 30 minutes. If you are spending too much time on the pump, please consult with a lactation provider so they can work with you on discovering what settings might work best for your body.

What’s the TLDR?

  • The flanges in your pump box are probably not going to work for you. Use a silicone nipple ruler like this one, a printable ruler like this one, or use the one included with your Amaris breast pump in order to ensure proper flange fit.

  • Gone are the days of automatically adding millimeters to your flange size. Pump for comfort. If you want to go up or down, do! Pick up a silicone insert kit like this one.

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