Flange Size Calculator

Created by Dominika Miszewska, MD, PhD candidate
Reviewed by Dominik Czernia, PhD candidate and Jack Bowater
Last updated: Sep 17, 2020

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, 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 birth.

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

How to measure your nipple size?

As we mentioned before, a correct breast pump flange fit allows easy milk pumping and prevents bruises, cuts, and other damages 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 diameter and the average flange diameter is between 24 and 27 millimeters. However, due to a great variety of nipples' sizes, you can find flanges measuring even 40 millimeters on the market. They most often have some range within which your breast pump flange fit.

How can you know is the flange size is not correct? There are some red flags which could alarm you. Just so you know, all of them can be a sign of mastitis, blockage of ducts, or any minor problem with breastfeeding, not necessarily 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.
  • Your nipple is stuck inside the flange and cannot move freely.

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

How to use flange size calculator?

For a perfect breast pump flange fit, start measuring your nipple with a ruler or a tape (do not measure areola!). Then put it 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 should be the flange compared with the nipple.

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