Flange Sizes for Pumping: How to Measure, Signs It’s Wrong, and Finding the Right Fit
Finding the right flange size for your breast pump is essential for comfort, milk flow, and protecting your nipple and breast tissue. At ForeMilk Lactation, we see many parents struggle with sizing — often because most pumps only include a “standard” size that doesn’t fit everyone.
What Size Do Pumps Usually Come With?
Most breast pumps come with 24 mm flanges (and sometimes 27 mm), but these sizes don’t work for everyone. Many people need smaller or larger sizes to pump effectively and comfortably.
How to Measure for a Starting Point
Flange sizing is based on the diameter of your nipple (not including the areola).
Measure your nipple in millimeters using a ruler or measuring tape.
Add 1–3 mm to that number to estimate your starting flange size.
Example: If your nipple measures 17 mm, you might start with a 19–20 mm flange.
Keep in mind — measuring gives you an approximation, not a guarantee.
Why Size Can Change Over Time
Your body changes during the postpartum period:
Fluid shifts after birth may temporarily increase nipple and breast size.
Breastfeeding and pumping can change tissue elasticity over time.
That’s why it’s important to reassess your flange fit periodically.
Signs Your Flange Size Might Be Wrong
You may need to adjust your flange size if you notice:
Pain or pinching during pumping
Rubbing or excessive friction on the nipple
Areola being pulled too far into the tunnel
Little or no milk despite good supply
Nipple swelling, redness, or blanching after pumping
What to Do If Your Flange Size Feels Off
Try a different size — most pumps sell replacement flanges or inserts in multiple sizes.
Let’s work together! Contact us to schedule an appointment and we can troubleshoot.
Use lubrication (like food-grade coconut oil) sparingly to reduce friction.
Recheck sizing every few weeks postpartum or if you notice changes.
The Right Fit Matters
A well-fitting flange supports comfort, milk flow, and long-term pumping success. At ForeMilk Lactation, we help parents find their perfect fit — so you can focus on your baby, not your pump.
