Fitting your Breast Pump

Written by Jennifer Clark IBCLC September 2026

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Reasons to ensure your breast pump fits properly: 

• A better fitting breast pump gets more milk 

• Ensuring the breast pump is comfortable and does not cause any pain or trauma to the breast/nipple 

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Most pumps now come with different flange inserts; it is key to fit your pump to maximise efficacy and comfort. If your pump does not come with the correct flange size you can usually order these online. 

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How to I size my pump? 

The most recent research suggests a closer fit to the nipple than previously advised. I use the term “to fit like a shoe” - not too big, not too tight but just a small gap around the outside of the nipple. Both nipples may not be the same size (“they are sisters not twins”) so ensure you size both to check. 

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1. Before feeding or pumping, measure the width of your nipple tip (not the base of the nipple) as shown in the picture. Choose the flange size closest to that measurement. Remember that each nipple may be a different size, so measure both. 

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2. When the pump is fitted and on you want your nipple to move in and out of the tunnel of the flange, the areola should not be pulled in, and your nipple should not rub on the side. 

See link: https://cdn.branchcms.com/GodJV07437-1548/docs/BIC_FlangeFitsGuide_WA_V3.pdf  ​

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Best fit – Only the nipple is pulled into the flange tunnel, and the nipple gently glides a little bit back and forth. It should also be comfortable, and milk should come out easily. It should feel like nothing or a gentle tug. 

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If the insert/size is too small the nipple will not move easily in the tunnel, and less/no milk comes out.  

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If it is too large it may hurt, make the nipple get bigger than it usually is (swollen) and less milk comes out. The areola may be drawn in and get swollen and damaged. 

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Tip: A thin layer of coconut oil or nipple balm on the bend of the flange can increase comfort. Pumping should feel good and get plenty of milk out! 

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If you need further help with this, please attend one of our breastfeeding cafes where we have a IBCLC present – See our ‘Lowestoft and Waveney Breastfeeding Support” Facebook page for week-to-week updates.