Why Size Matters
Finding the Right Flange Size
By Anna Rademaker, IBCLC, LMT | Sacred Mama Denver
Did you know that using the wrong flange size can lower your milk output and make pumping painful? Most pumps come with 24mm or 28mm flanges by default, but many parents need much smaller or larger sizes. The range on the market goes from about 10mm up to 36mm — every body is different!
Your flange should fit so that your nipple moves freely in the tunnel without too much areola being pulled in. It should not pinch, rub, or hurt. Pumping should feel comfortable — never painful.
Use a flange ruler (see image below) or the Flange FITS Guide to measure: measure your nipple diameter (not the areola) and add about 1–2mm for swelling during pumping. Many parents are surprised to find they need a smaller size than what came with the pump!
4 Steps for a Better Fit:
Measure your nipples before pumping.
Test different flange sizes.
Watch how your nipple moves during pumping.
Adjust or replace flanges for comfort and better milk flow.
A good flange fit can help you get more milk with less pain.
If pumping hurts — it’s a sign you need help! Book a consult with me, Anna Rademaker, IBCLC, and let’s make pumping more comfortable and effective for you.
Note: This is not medical advice — always talk with your lactation consultant for a personalized fit plan.