
Common breastfeeding issues can stem from a lack of knowledge, pain tolerance, low milk supply, latching issues and so much more. But many moms are unaware of the consequences of having a breast pump flange size that is too big or too small, and how to properly measure it.
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It won’t even cross their mind, because we hear from society “it will hurt but it will get better” so we expect any pain during the process to be the pain they are talking about. If my in-laws did not warn me about the importance of how to measure my nipple for the right breast pump flange size, I would’ve had low milk supply for weeks.
PROPER FITTING = SUCCESSFUL PUMPING
Wait, what is a flange?
I am here to help you figure out the nipple to flange size guide: does flange size affect milk output, what happens if flange sizes are too big, signs of wrong flange size, how should a breast pump flange fit, are there bigger or smaller sizes?

The part of the breast pump that suctions a nipple to express breastmilk; a visual above.
Why Is Proper Flange Fitting SO Important?
An Improper flange fit could be one of the reasons you decide to stop breastfeeding. YOU DON’T KNOW WHAT YOU DON’T KNOW! And a lot of women, including myself did not know this was an issue until my second week of breastfeeding.
This flange size issue made the whole experience uncomfortable, my flange was way too big. So it was pulling on my areola more than stimulating the area around the nipple that can express the right amount of milk. My flange was 7 sizes too big!

A Flange Too Small
- Cause a clogged milk duct due to constriction
- A chapped, discolored nipple
- Pinching/Uncomfortable
A Flange Too Large
- Pulling of Areola
- Not enough nipple stimulation to express the necessary milk supply
A Comfortable Fit Flange Should
- Should pull a minimal amount of aerola, majority of the nipple
- Wiggle room to adjust nipple if necessary
- Continuous milk being expressed after let-down has started
IF YOU HAVE THE RIGHT-SIZED FLANGE and it is still bothersome or feels like a burning sensation from the suction I recommend applying baby-safe nipple butter, or lanolin to avoid friction while pumping. These two products are safe to feed the baby after applying to the nipple (why I emphasized baby-safe).

How To Measure My Nipple For Correct Flange Size?
This was the part that always confused me, but I am going to simplify it and make it easy for all of us!
Take a ruler or measuring tape and place it under the nipple. Remember the areola is the OUTSIDE area around the nipple, we are not including the areola in our measurements.
It is possible to have one nipple bigger than the other, another thing to keep in mind. So you will want to measure both sides. Also I do not recommend measuring prenatally, your nipples can swell and change size. If you want to be safe for the first days, I recommend ordering a size or two bigger for better preparation.
Take the ruler/measuring tape and place it under the nipple where you are able to read the numbers ACROSS perfectly. Place the ruler under where you would start and mark with your finger where the right side of your nipple ended.
The little tiny lines on the ruler between cm’s are mm’s, you are going to count the lines and from that measurement, you are going to add 4 to that number. And that is the measurement of the flange you will need.
OR
Every 1cm is 10mm, so that is also another way to make measuring easier.

How Do You Know Which Flange Size To Use?
I used to think you had to measure the nipple from the base out, I was very confused but that was not the case because we are measuring the diameter; under and across.
If you measure out 17mm on the ruler your flange size is 21mm
Ruler: 20mm -> Flange Size: 24mm
23mm -> 27mm
26mm -> 30mm
32mm -> 36mm
You are simply adding 4 to the ruler size. Adding 4 mm will give your nipple enough space to comfortably pump. Unfortunately, breast pumps only come in 2 sizes 24mm + 27mm. If these aren’t my sizes what do I do?
My Pump Brand Doesn’t Have My Flange Size, What Do I Do?
My measurement on the ruler was 14mm, so I ordered the 17mm flange. The Spectra nor Medela brands had this size available, so I ordered them on amazon and worked perfectly.


For the Spectra flange I had to order inserts on amazon(made of silicone, which made my pumping sessions more comfortable).


My Medela brand was a manual pump, but this is sold for the regular and manual pump, I was able to find a flange in 17mm on amazon also.
After Pumping
Your breasts should feel soft and emptied; in the near future, your milk supply should remain the same or increase if you are staying consistent with pumping (& the right flange size). Contact your lactation consultant or doula if you continue to have issues with breastfeeding!
Pumping Hack
If for some reason you are experiencing an inconvenience with holding your flanges while pumping, or a mid-tier pumping bra that was probably too expensive to purchase, do I have the hack for you!
All you need is a nursing bra with clips and this will change your life! You can have a nursing bra and a pumping bra all in one, without the mess or a specific flange to fit.
