you have made the decision to pump from the get-go, you’re getting ready to order your pump to bring to the hospital, OR you already know that you want a pump to incorporate into your breastfeeding journey.

P.S. — remember, over here we refer to “breastfeeding” as an umbrella term, meaning nursing OR pumping, or any combination of the two!

but WHEN do you actually need to measure your nipples to figure out the most accurate flange size for your body? you want to be prepared, and don’t want to wait for the correct flange sizes to be sent to you. like SOS HELP 🚨

WHAT YOU NEED TO KNOW ABOUT FLANGE SIZING —

this is one of the most impactful actions that you can do to set yourself up for a successful pumping journey!!! the flange is the tunnel diameter size of the funnel piece that fits on your breast. you’ll find that typically and historically, you’ll receive probably 24-28mm sizesis with a breast pump and all it’s equipment.

an accurate flange size does 2 BIG things👇🏼

• gives you amore comfortable pump session that decreases nipple trauma and pain
• allows for more milk to be expressed, leading to feeling more empty, and increasing supply
  
  

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LEAVING THESE RESOURCES FOR YOU BECAUSE THESE ARE THE ITTTT GIRLS FOR FLANGE SIZING LIKE A DAMN PRO —

FREE nipple measuring tool — find your flange size DIY style by printing out this downloadable guide, from 8mm-27mm. i gotchu on getting started to the right equipment your body needs!

$9 ultimate flange catalog — your list of flanges across the entire market: flange inserts, hard plastic, silicone, how to pick your equipment for your most comfortable pump session and my hot tips + tricks for flange sizing as accurately as possible (as a lactation counselor who helps parents pump with confidence to feed their babies).

1:1 virtual consult — this is where you meet with me via your phone, cozied up in your fav blanket at home, we get to the down and dirty on your flange size, AND your pumping goals. increasing milk supply, emptying fully, weaning with more intention (less rush), i’m all yours to get to where you want your breastfeeding journey to feel like.

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but what we know now (and honestly what lactation counselors specifically focused on exclusive pumping have been trying to say for so freaking long) — one of the newest studies has shown that most lactating parents need a size SMALLER than 21mm be successful in their pumping journey. omg like finally this is in writing and showing us the proof we already know!!! READ THE STUDY HERE

so what this means is that we need to measure our nipple sizing, not just assume a size, because the standard 24mm is more than likely too large. i can confirm this, because i had ONE single client in 2025 that was more than 21mm 👀 and ONE single client who was using a size too small — everyone else was using a flange size that was too large!!!

SO WHEN THE HELL DO YOU MEASURE TO HAVE THE MOST ACCURATE SIZE TO YOUR BODY?

when you find out you’re pregnant?
at 30 weeks?
when you go into labor?
the second you need to start pumping?

the shortest and best answer — after birth. there are SO many hormone fluctuations that happen when your placenta is “birthed”, which impacts your milk supply and lactation processes to get underway. (wanna learn more about lactation as a whole and how to make this work best for your pumping journey? find all the details about the pumping course HERE)

if you’re pregnant, you’ll measure your nipples after birth. and even better if you’re able to after the 1-2 hours you’ll spend skin to skin with babe (even if you don’t plan to nurse, this is HUGE when it comes to establishing your milk supply)

• this is because your nipples may increase in size after birth (very normal when lactating)
• and may also decrease in nipple sensitivity! pregnancy nipple pain and discomfort is WILD, and this typically improves drastically after birth

if you’re later on in the postpartum period, you’ll measure before your pump session, and 10 minutes into your pump session. this is because your nipples can shift and change during pumping, and this accounts for potential elasticity, or inflammation from the nature of pumping.

and remember to measure both sides!!! did you know that your nipples can adjust in size further along in your breastfeeding journey, and each side can measure differently?!

snag the nipple measuring tool and directions on HOW to actually do this correctly HERE!!!

you can probably expect your nipples to be between 13mm-19mm sizes (especially right after birth). these are the most common and popular sizes for REAL folks body anatomy (not what pump companies automatically provide you with). but i do have to shout out my friends over at Pumpables — they are one of the first ever companies that allows you to choose your flange size when ordering your pump!!! literally this is how all pumping equipment should be in 2024 — brb gonna go and be so vocal about this so you can have access to all sizes and equipment in your pumping journey 😘

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related blog posts that i think you’ll seriously love —

• the how, when and why of collecting (aka harvesting) colostrum antenatally
• the most underrated and (mostly) free baby shower and postpartum gift that you’ve probably never heard of
• a peek into my DMs: “can i increase my supply at 3/6/9/12 months postpartum?”

what other flange sizing questions do you have? what will make this measuring process easier for you?
xoxo, Bethany | Certified Lactation Counselor | Your Overproducing Exclusively Pumping Mama