Flange Size Calculator

Created by Dominika Śmiałek, MD, PhD candidate
Reviewed by Dominik Czernia, PhD and Jack Bowater
Based on research by
Irene Murphy Zoppi Correctly Fitting Breast Shields: A Guide for Clinicians Neonatal Intensive Care Supplement/ Georgia Department of Public Health (2012)
Last updated: Sep 14, 2022

Are you planning to use a breast pump? Take a moment to use this flange size calculator and find the diameter of your perfect flange. By using the correct size flange you avoid numerous complications, such as pain, abrasions, and discomfort, while pumping breast milk. In the following article, there is information on the nipple size measurement technique, breast pump flange size differences, and the uses of a breast pump flange.

As we all know, mom's milk has a lot of positive impacts on the child. 🤱🏽 It promotes its harmonic development (check out our height percentile calculator to assess that), makes the child smarter, improves their immune system, and helps to avoid obesity. Sometimes it's necessary to draw milk instead of direct breastfeeding, in, for example, prematurely born babies - and that's where this flange size calculator comes in use.

Breast pump flange purpose

The breast pump flange is funnel-shaped piece of plastic that is placed onto your nipple during pumping. We also know it as a breast shield, and it allows a vacuum seal to be formed. This causes milk to be drawn from your breasts and delivered through the flange to the pump.

While the average flange is between 24 and 27 millimeters (0.95 - 1.06 in) wide, nipple size can vary significantly. The correct flange size prevents nipple damage and allows the pump to extract the milk efficiently. Nipple damage may lead to painful duct blockage, which is especially common in women just after baby due date.

With this flange size calculator, you can prevent these unwanted situations from happening.

How to measure your nipple size?

As we mentioned before, a correct breast pump flange fit allows milk to be easily pumped and prevents bruises, cuts, and other damage to the nipple. To measure your nipple, take a ruler or a measuring tape and check your nipple diameter (without the areola).

Flange measurement

Breast pump flange size

A typical flange should be 3-4 millimeters larger than the nipple's diameter, and the average flange diameter is between 24 and 27 millimeters. However, due to the great variety of nipple sizes, you can find flanges measuring up to 40 millimeters on the market, so you should be able to find the best breast pump flange fit.

How can you tell if the flange size is not correct? There are some red flags which should alarm you. Just so you know, all of them can also be a sign of mastitis, blockage of ducts, or any minor problem with breastfeeding, and are not necessarily problems caused by the flange itself. You should be alarmed by:

  • Pain in your nipple;
  • Some parts of areola inside the tunnel of the breast pump;
  • After pumping, you feel that there are still areas with milk inside; and
  • Your nipple is stuck inside the flange and cannot move freely.

🧑‍⚕️ In this part, we consider it important to remind you to keep practicing regular breast self-checks during breastfeeding to check if there's breast cancer risk. If anything seems worrisome, go to your physician for a breast ultrasound.

How to use flange size calculator?

For the perfect breast pump flange fit, start measuring your nipple with a ruler or tape (do not measure the areola!). Then put your measurement into the tool and wait for the results. The correct flange diameter is 3 to 4 millimeters larger than the nipple. For example, if your nipple is 19 mm in diameter, then the perfect flange is 22 - 23 mm.

If you're still not sure, check out the image below this breast pump flange size calculator. It shows how big the flange should be when compared to the nipple.

Dominika Śmiałek, MD, PhD candidate
Nipple diameter
How big should your flange be?
How to measure your nipple size?
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