How to Measure for Accurate Nursing Bra Sizing

Ensuring correct nursing bra sizing before buying is key for optimizing each bra’s design and features.


Most women notice that their regular bra begins to feel tight sometime around the second trimester of their pregnancy. This is a good indicator that it’s time to purchase some maternity and nursing bras as you prepare for the rest of your pregnancy and then breastfeeding, but you may not know where to start. Nursing bra sizing doesn’t differ from sizing for regular bras, though it is sometimes recommended to purchase your nursing bras in a cup size or two up to account for fuller breasts during pregnancy and while breast milk feeding.

The Importance of Correct Nursing Bra Sizing

Comfort and functionality are important features to look for in a nursing bra, especially as your body changes. Ensuring correct nursing bra sizing before buying is key for optimizing each bra’s design and features. While every woman’s body is different, taking extra precautions by steering clear of things like lace and underwire can help alleviate discomfort and aggravation while your breasts are producing milk for your new baby.

Approximately 80% of all women wear the wrong size bra - about 70% wear bras that are too small and 10% wear bras that are too large. This may adversely affect your breast milk supply, as it is widely believed that bras that are too tight or have underwire that digs into your breast tissue could block one or more milk ducts. A blocked milk duct can be troublesome and eventually lead to infection or mastitis if not treated right away by a healthcare professional. Proper nursing bra sizing can be quite easy to measure using the directions below, so you can find the most comfortable fit for your needs.  

Take Your Measurements and Use Our Nursing Bra Size Chart

Measuring yourself to determine your bra size will give you a starting point before you begin trying on nursing bras. You’ll need a few things handy to get started:

What You’ll Need

  • Measuring Tape

  • Blank paper

  • Pen

  • A non-padded bra reflecting your true shape

  • A full-length or bathroom mirror

Once you’re ready to begin measuring, follow these steps to figure out your current bra size:

Find Your Rib Band Measurement

  • Pull the measuring tape around your back and beneath your armpits. The measuring tape should lie above your breast tissue.

  • While looking into your mirror, ensure the measuring tape is parallel to the floor around your back. Confirm that there are no fingers under the tape and exhale.

  • Write down the measurement that you see. If you are between sizes, round up or down to the nearest full, even number (such as 34, 36, or 38). This is your rib band measurement.

Now, Measure Your Cup Size

  • Adjust the tape so it is still wrapped around you, but now measures around the fullest part of your breasts.

  • Hold the end of the measuring tape at the side of your chest and grab both ends of the tape in one hand.

  • Use your free hand to press the measuring tape between your breasts and into your chest.

  • Write down the measurement that you see. Note that this will likely be a larger measurement than your rib band, but should provide an accurate cup size.

Subtract your rib band measurement from your cup size measurement – for example, 36 – 32. The difference (4) should be matched with the corresponding letter in the nursing bra size chart below:

















Your bra size is your original rib band measurement (36) with the letter matching your cup size (D), so our example bra size would be 36D.

Finding the Right Nursing Bra

Once you find the perfect fit, you may want to try our Ultimate BodyFit Bra, made with soft four way stretch material and convenient drop-down cups with one-handed nursing clips. This bra also provides extra support for your back with flexibility to adapt to mom's changing size during pregnancy and postpartum.

Medela’s maternity and nursing apparel was designed to meet your unique needs 24 hours a day, 365 days a year. Our apparel naturally adapts to your changing shape and keeps you comfortable while conveniently allowing you to pump or nurse whenever needed. Throughout each step of your breast milk feeding journey, Medela is proud to provide exceptional fit, comfort, and functionality to moms around the world.