Silicone Nipple Ruler - Instructional Guide

By: Sabrina Granniss, IBCLC


6 min

Are you struggling to find the perfect flange fit when using your breast pump? Look no further! Your breast comfort and milk output are helpful indicators of whether you have the correct shield or flange size. A proper flange size results in optimal milk removal and overall comfort during and after pumping. But how do you determine the best fit for you? Luckily, Legendairy Milk's Nipple Ruler tool is here to help. End flange discomfort or guesswork, get the perfect fit and optimize your pumping experience.

Too Big

  • Discomfort or pain
  • Stretches and pulls areolar tissue into the tunnel of your flange
  • You may have a hard time keeping the flanges from staying suctioned to your breast while the pump is on
  • Your milk removal will not be as effective and can leave you feeling still full after pumping
  • Can lead to nipple damage or plugged ducts from the wrong flange fit.

Too Small

  • Your nipple may rub or seem to get stuck on the flange walls as you pump, causing soreness. First, try using a lubricant like coconut oil or Pumping Spray to help the nipple glide more freely in the flange tunnel.
  • Can cut off blood circulation to the nipple and cause blanching of the nipple and sharp pain called a vasospasm. This pain can occur between pumping sessions, as well as itching or a burning sensation with continued use of a flange that is too small.
  • Not getting a lot of milk removal during the pumping session
  • Cracked or damaged nipples

Just Right

  • Pumping is comfortable for the whole session and in between sessions.
  • You see sprays of milk while you pump
  • May reduce the total time you need to pump in a session to feel “empty”, although you are never totally empty since as you remove milk, more milk is made.

Tips for using the Legendairy Milk silicone nipple ruler

Use your Nipple Ruler tool while in front of a mirror to help you see how you are measuring. Snap a photo or video with your phone to re-watch how you measured your nipple and determine if the ruler was well placed for taking your nipple measurement.

To get the correct sizing, you want to measure only the nipple, not the areola, which is the darker area around the nipple. If your nipples are flat or inverted, try stimulating the nipple so it is more erect for measuring. If it doesn't, it is ok. You can still measure your nipple with a standard ruler or the Legendairy Milk Nipple Ruler.

The Nipple Ruler provides two ways to measure your nipple. On the long edge of the tool is a millimeter measurement ruler guide. The rest of the guide has cut-out circles to fit your nipple inside of for finding your measurement. to measure the diameter of your nipple.

How to measure your nipple using the ruler:

  1. Hold the ruler with 0 lined up with the edge of the nipple where it meets the areola.
  2. Where the other edge of your nipple is indicates the number in millimeters of your nipple diameter.
  3. Nipples are not always the same size. Measure each nipple individually since you may not get the same measurement for the left and right.
  4. Hold the tool flat so it is not bending which may manipulate the measurement you get.

Using the circles on your silicone measuring tool:

  1. Center a circle close to your nipple diameter over your whole nipple.
  2. Your nipple should fit completely inside the circle. The flexibility of the tool comes in handy for comfort while doing this.
  3. Make sure you can see your entire nipple inside the circle and right where it meets the areolar tissue.
  4. The number in millimeters indicates your nipple diameter.
  5. Don’t forget to measure each nipple individually since you may not get the same measurement on the left and right sides of your chest.

When is the best time to measure your nipples

Our nipples may change in size from the beginning to the end of a pumping session. As you pump, the nipple swells and becomes larger in diameter. Feeding directly at breast and hand expression affects your nipple differently than with using a pump, and there is more swelling of the nipple while pumping. (1)

If you measure your nipples before beginning to pump or before you have your baby, you will have an idea of size, but may not find the perfect fit until after your baby has arrived and you begin pumping. You should have a few sized flanges on hand to try out after your baby arrives. You should have the size you measured and flanges smaller and larger than your measurement.

Keep in mind if you have been pumping with an incorrect size flange, it can cause swelling of your nipple. The measurement you get could change as swelling decreases.

Your nipple measurement may also change over time. Several months into using your breast pump and feeding your baby, it may be necessary to measure each of your nipples again. A correctly fitting flange allows your nipple to move freely in the tunnel of the flange without pulling in areolar tissue.

In one study of mothers expressing milk for their preterm babies, 77% of the women needed a larger flange size as time passed. (2) 

Nipple shape, size, and elasticity when flange sizing

Breasts and nipples are many different shapes and sizes. Pumping is not a one-size-fits-all activity.  Finding the right flange fit for you may mean you need to order flanges that were not included with your pump. Most pumps come with size 24mm and 27mm flanges, which are not the most common size nipples of breastfeeding moms.

Breast tissue elasticity is normal and varies among moms, but elasticity may be exaggerated if a flange is not the right fit. If you have more elasticity, flange inserts can be placed inside your pump flange for a more comfortable fit and experience. Having an IBCLC who can guide you through finding the right flange fit for you may be helpful if you are having a tricky time getting that comfy and most effective flange fit on your own.

Many people find a flange that is the size of their nipple is a good fit, but you may need to experiment to find the best match. It can be complicated, and having an IBCLC who is flange-educated can help you evaluate all the factors involved in pumping and help you find your perfect match.

Legendairy Milk’s silicone Nipple Ruler tool is more comfortable than hard plastic tools. It is more stable than a paper ruler and is super soft against your skin, helping to mold it to your uniquely shaped breast for more accurate measuring. Wash your measuring tool with warm, soapy water before and after each use. 

End pumping discomfort and begin being able to enjoy your pumping experience by using the correct flange size for your nipples. The Legendairy Milk Silicone Nipple ruler can help you find your perfect flange fit. Use the ruler edge or the circle cut-outs to take accurate measurements at each breast. The right size flange will feel good, remove milk effectively and efficiently, and make your pumping experience a breeze. 


Related Blogs


  1. Francis, J., & Dickton, D. (2019). Physical analysis of the breast after direct breastfeeding compared with hand or pump expression: A randomized clinical trial. Breastfeeding Medicine, 14(10), 705-711.
  2. Meier et al, Choosing a correctly-fitted breast shield for milk expression. Medela Messenger. 2004;21:8-9


Francis, J., & Dickton, D. (2019). Physical analysis of the breast after direct breastfeeding compared with hand or pump expression: A randomized clinical trial. Breastfeeding Medicine, 14(10), 705-711.

Meier et al, Choosing a correctly-fitted breast shield for milk expression. Medela Messenger. 2004;21:8-9

Wambach and Spencer, Breastfeeding and Human Lactation 6th edition, 2021; 375


I’d like to buy one

Dianna Castillo

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