How to Find Your Nursing Bra Size at Home

Quick answer

Measure your nursing bra size at home by wrapping a soft tape around your ribcage directly under your bust for the band, then around the fullest part of your bust for the cup, and subtract the band from the bust measurement. Measure toward the end of a feed when breasts are softer, and round the band to the nearest even number. Recheck once more after a week, because milk supply and ribcage shape shift in the first months.

Your bra size during breastfeeding is rarely the same as your pre-pregnancy size, and guessing usually ends in a band that rides up or cups that dig in. A short at-home measuring session gives you a reliable starting point before you order anything.

The method below takes about ten minutes and needs only a soft tape measure, a mirror, and a well-fitting unpadded bra or a light top. It is the same logic a fitter uses, translated into steps you can repeat whenever your body changes.

Before you measure: timing and tools

Measure toward the end of a feed or pump session, when breasts are at their softest. Measuring right before a feed inflates the bust number and pushes you into a cup that gapes a few hours later. If your supply is still regulating, expect to remeasure every four to six weeks.

Use a soft, non-stretch tape and wear a thin, unpadded bra or a fitted top so the tape follows your shape rather than compressing it. Stand in front of a mirror so you can check that the tape stays level all the way around your back.

• Keep the tape snug but never indenting the skin.
• Write both numbers down immediately; small differences matter.

Step 1: Find your band measurement

Wrap the tape around your ribcage directly under your bust, keeping it parallel to the floor. Breathe out normally and read the number where the tape meets. This is your underbust measurement, and it becomes the band size.

If the number is odd, round down to the nearest even number for a snugger band, or up if you prefer a little more room. A band that feels tight on the loosest hook is usually right, since bands relax with wear and your ribcage can change shape during breastfeeding.

• Common mistake: measuring over a padded bra or thick clothing, which adds phantom inches.

Step 2: Measure your bust at the fullest point

Wrap the tape around the fullest part of your bust, usually across the nipple line, without pulling tight. Keep the tape level and let it rest on the tissue rather than pressing in. Read the number at the center of your chest.

Do not lift your arms while measuring; that changes the shape of the bust and skews the number. If you are between feeds and feel uneven, measure both sides and use the larger measurement for the cup.

• Common mistake: pulling the tape tight because it feels more secure, which understates the cup.

Step 3: Calculate your cup size

Subtract your band measurement from your bust measurement. Each inch of difference generally equals one cup size, so a one-inch difference points to an A cup, two inches to a B, three to a C, and so on. This is a starting point, not a verdict, because cup fit also depends on breast shape and how much coverage you want.

Nursing bras often run differently from standard bras, especially wireless styles. If your calculation lands between two cups, start with the larger cup and adjust the band if needed, since a too-small cup is the most common cause of discomfort during feeds.

• Common mistake: assuming your pre-pregnancy cup size still applies; most nursing mothers go up one or two cup sizes.

Step 4: Check the fit on your body, not just the numbers

Put the bra on the loosest hook and check three points: the band should sit level and stay put when you lift your arms, the center front should rest against your ribcage, and the cups should hold all your breast tissue without spilling or gaping. If the band rides up, go down a band size; if the cups dig in, go up a cup.

A wireless bralette can feel very different from an underwire style, so judge each one on its own terms. For a wireless option, look for a band that stays level and cups that follow your curve rather than pressing it flat.

• Try the bra on over a thin top if you are unsure how much coverage you want.

Step 5: Recheck after a week and after supply settles

Your size in the first weeks is not your size at three months. Measure again after a week, then again once your supply feels stable, and adjust one variable at a time so you can tell what actually changed. Keep the measurements in your phone notes for quick reference.

If you are ordering online, check the size options the brand offers before you commit. Some styles list only a single size option, which means you need your measurement to be accurate rather than relying on a range.

• Common mistake: buying several bras in one size before your supply regulates.

Your six-step nursing bra measuring routine

1. Time it after a feed: Measure when breasts are softest, usually at the end of a feed or pump session. Checkpoint: if you measured right before a feed, wait and redo it.
2. Measure the underbust: Wrap a soft tape directly under your bust, keep it level, and round to the nearest even number. Checkpoint: the tape should sit snug but not leave a mark.
3. Measure the fullest bust point: Run the tape across the fullest part without pulling tight, arms down. Checkpoint: if the tape slips, restart rather than averaging.
4. Subtract band from bust: Each inch of difference equals roughly one cup size. Checkpoint: when between cups, start with the larger one.
5. Try the bra on the loosest hook: Check that the band stays level, the center front touches your ribcage, and cups hold all tissue. Checkpoint: band riding up means go down a band size.
6. Remeasure in a week: Repeat the process once your supply settles and note any change. Next step: adjust one variable at a time, then reorder if needed.

Nursing-friendly styles worth measuring for

• Viana Verde Longline Bralette: Wireless and unpadded, made from soft sage-green lace with floral details, and designed to adapt to your curves. A wireless, unpadded bralette is a forgiving choice while your size is still shifting, because it follows your shape instead of forcing it.
• Saga Navy Underwire Bra: An underwire bra with deep-cut cups, navy floral lace, black straps, and adjustable back straps. If you want more support and a defined shape, an underwire style with adjustable straps lets you fine-tune the fit as your measurements change.
• Cayenne Bralette: A wireless bralette with swirling edges, adjustable shoulder straps, and an adjustable back closure. Adjustable straps and a back closure give you room to tighten or loosen the fit without changing sizes.

Measuring at home takes ten minutes and saves you from a drawer full of bras that almost fit. Start with your underbust and bust numbers, test one style on the loosest hook, and remeasure as your body changes. If a bra feels wrong, change one thing at a time until the band stays level and the cups hold you comfortably.