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Flange Size Guide for Breastfeeding Mothers

breast flange size



Flange Size Guide for Breastfeeding Mothers

Breastfeeding can be a beautiful and fulfilling experience for mothers and their babies. However, it can also be challenging, especially for new mothers who are still getting used to their new role. One of the biggest challenges that new mothers face is finding the right size of flange for their breastfeeding needs. A flange is the part of the breast pump that fits over the nipple and areola to create suction and express milk.

It’s important to choose the right flange size as it can affect the comfort and efficiency of the pumping experience. A flange that is too small can cause discomfort, pain, and even nipple damage, while a flange that is too large can be ineffective and cause milk to leak. In this flange size guide, we will provide all the information you need to help you find the perfect size for your breastfeeding needs.

Understanding the Anatomy of the Nipple and Areola

Before we dive into finding the right flange size, it’s important to understand the anatomy of the nipple and areola. The nipple and areola are the two parts of the breast that are essential for breastfeeding. The nipple is the part that sticks out, while the areola is the dark-colored skin surrounding the nipple.

The size of the nipple and areola can vary greatly from mother to mother, and can even vary between the two breasts. It’s important to measure both nipples and areolas to ensure that you have the correct size for both.

Measuring Your Nipple and Areola

To determine the correct flange size, it’s important to measure both your nipple and areola. The easiest way to do this is to use a measuring tape or a ruler. Start by measuring the diameter of your nipple at its widest point. This is the most important measurement, as a flange that is too small will cause discomfort and pain.

Next, measure the diameter of your areola at its widest point. This measurement is important because it will help you determine the correct size of flange for your particular anatomy. If your nipple is small and your areola is large, you may need a larger flange to accommodate both.

Flange Sizes: What’s Available and What to Choose

Breast pump manufacturers offer flanges in a variety of sizes, ranging from 21mm to 36mm. It’s important to choose a flange size that is appropriate for your nipple and areola size. If you’re unsure what size to choose, it’s best to start with the smaller size and work your way up until you find the right size for you.

Here’s a general guide to help you choose the right flange size:

  • 21mm flange: suitable for nipples measuring less than 20mm
  • 24mm flange: suitable for nipples measuring 20mm to 24mm
  • 27mm flange: suitable for nipples measuring 24mm to 27mm
  • 30mm flange: suitable for nipples measuring 27mm to 30mm
  • 36mm flange: suitable for nipples measuring 30mm to 36mm

It’s important to note that these are just general guidelines and not all mothers will fit into these categories. If you’re still unsure about your flange size, it’s best to consult with a lactation consultant or your healthcare provider for personalized advice.

Tips for Choosing the Right Flange Size

Here are some tips to help you choose the right flange size for your breastfeeding needs

  1. Measure your nipple and areola size: As mentioned earlier, it’s important to measure both your nipple and areola size to determine the correct flange size. Don’t rely solely on the general guidelines as they may not apply to your specific anatomy.
  1. Try different sizes: If you’re not sure what size to choose, don’t be afraid to try different sizes. Start with a smaller size and work your way up until you find the right size for you. You can also try different shapes of flanges, such as the round or the funnel shaped, as some mothers find that one shape works better for them than the other.
  2. Consider your pumping frequency: If you plan on pumping frequently, it’s important to choose a flange that is comfortable and efficient. A comfortable flange will help you avoid discomfort and pain, which can make pumping less enjoyable and even cause you to give up breastfeeding.
  3. Check for proper suction: Once you’ve chosen a flange size, make sure to check for proper suction. A proper suction means that the flange is creating a seal around your nipple and areola, allowing for efficient milk expression. If the flange is too small, the suction will be insufficient, and if it’s too large, the suction will be too strong, causing discomfort and pain.
  4. Replace your flanges regularly: It’s important to replace your flanges regularly as they can become stretched out or worn down over time, affecting the suction and comfort. A good rule of thumb is to replace your flanges every three to six months.


Choosing the right flange size is an important aspect of breastfeeding, and it can make a big difference in your pumping experience. By following the tips and guidelines in this flange size guide, you can ensure that you find the perfect size for your breastfeeding needs. Don’t be afraid to try different sizes, and don’t hesitate to consult with a lactation consultant or your healthcare provider for personalized advice. Remember, the most important thing is to find a flange size that is comfortable, efficient, and helps you reach your breastfeeding goals.



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Breast shield: Choosing the right one for you

Did you know that breast shields ( flanges) come in different sizes? Many mummy experience inefficient pumping session, and the reason is usually because of wrong breast shield size. Many breast pumps ship with size 27mm or 28mm in Singapore; however, that doesn’t mean that everyone will fit that size (we don’t all wear the same sized shoes, after all). There are breast shields on the market ranging in size from 15mm to 36mm!

Follow this simple guide to determine your breast shield size but first thing first

Pump for 5 minutes, and then measure

It’s a common misunderstanding to measure your nipple before you start pumping, but you actually have to measure the nipple after you pump. The reason is simple. The nipple swells while pumping, and since the rate of swelling varies between women, it’s important to take this swollen measurement to select a comfortable shield size. Grab the shield that came with your pump, assemble it to the milk collection kit and then pump on a low setting for 5 minutes, so the nipple swells. You might even express milk while doing this (if this is your first time pumping, be sure to use the lowest vacuum setting to avoid any pain or discomfort).

Measure the diameter of the nipple at the base of the nipple

After your nipple has swollen, measure the diameter of the nipple at the base of the nipple. Be careful not to include any areola in the measurement. Gently lay a ruler onto the areola next to the base of the nipple so the measurement lines are visible when looking straight at the breast. This can be tricky so some women find that doing it in front of a mirror or using a smart phone in selfie mode is helpful.

Select a shield size 2-3mm larger than your nipple diameter

To allow the nipple to move freely within the flange while pumping and to avoid any pain or discomfort (or worse – blisters!) from rubbing, select a shield size that is 2-3mm larger than the diameter of your nipple. For example, if your nipple measures at 18mm, you would want to try the 20mm shield. It’s important not to go too large either because excess areola can be drawn into the flange, causing discomfort, pain, or even constriction of milk flow.

Signs your breast shield may be too small

  • Painful rubbing of nipple in flange.
  • Nipple not moving freely inside of flange.
  • Redness of the nipple.
  • Whiteness of the nipple and/or a white ring around the base of the nipple.
  • Little milk is being expressed.
  • General discomfort while pumping.

Signs your breast shield may be too large

  • Excess areola is drawn into the flange or even up and around the nipple. Note that a small amount of areola may enter the flange for some women; however, it should never be uncomfortable or painful.
  • Sensation of pulling and/or pulling pain.
  • Nipple is pulled to the end of the flange.
  • Shield falls from the breast while pumping.
  • Little milk is being expressed.
  • General discomfort while pumping.

Size that is just nice

  • A properly sized breast shield should be very comfortable.
  • You should barely be able to feel it while pumping.
  • Just a gentle tugging sensation on the nipple and nowhere else.
  • You should not see any excess areola being drawn into the flange
  • Should not feel a pulling sensation or pain while using your breast pump.
  • After your pumping session, your nipple should be free of any redness or whiteness.
  • Pumping should be pain-free

Additional factors impacting breast shield size

breast shield

Although the above instructions provide a good indication of the size of breast shield you will need, there are few things to consider:

  • Every woman’s body responds differently to pumping. It is possible your measurements before pumping might change during pumping, therefore we suggest taking measurements of the swollen nipple 5 minutes after pumping.
  • Your measurements might be different throughout the day. For example, you might be fuller in the morning after going a few hours without pumping and/or feeding at night, warranting a larger size. You might also be smaller in the evening after consistent pumping or feeding throughout the day.
  • You might be larger at the beginning of a pumping session, and smaller after some milk has been expressed.
  • Your measurements might change after your milk supply is well-established (about 10 weeks postpartum).
  • One breast may need a different sized breast shield than the other.

However, you should not follow this guideline blindly because the info graphic merely relies on nipple diameter only. In addition to nipple diameter, you should also consider the following factors:

  • Check how your nipple moves while pumping.

The nipple should move freely and it should not rub the side wall of the flange. You may see a little bit of areola gets pulled, but not the whole areola. And your nipple should not hit the back wall of the breast shield.

  • Comfort

Even if you think you already choose the best breast shield size, but you feel uncomfortable / painful while pumping, that means something is not right. Try to size up or down. Nipple redness / or sore feeling after pumping is also an alarm that you may need to choose different breast shield size.

  • Effectiveness of pumping

If you feel you breast is not emptied after pumping, you may suspect that you don’t use the correct breast shield size (note: various factors can affect this, breast shield size is just one of possible reason).

  • Breast tissue / elasticity

Some women has a very elastic tissue so that the skin will get pulled easier. In this case, it is possible that pumping makes nipple get elongated so much until it hits the back wall of the flange. For this case, using breast shield with longer ‘tunnel’, or using smaller insert in bigger breast shield may help.

SLB Nipple Ruler

Simply print it out, fold along the line, and carefully cut out the circles.

The nipple ruler works on both US Letter and A4 paper sizes. Make sure you select “full size” or “100%” in your print menu (don’t “scale to fit”). You can also print it on larger sizes like US Legal or A7, but you might have to trim off the extra

Nipple ruler
Flange size

At the end of your pumping session, use the circles to measure the diameter of your nipple at the base. You should select a size that is snug, but not constricting, around your nipple.

Here’s another Nipple Ruler we found from MayMom

breast shield

If you have more questions or need further help with breast shield sizing, reach out to a Certified Lactation Consultant. In the long run, it’s worth taking the time to determine the breast shield size that’s right for you. You’ll benefit by maximising your pumping sessions so you can get back to what matters most – the little one you’re pumping for!