Measure at a mid-point between feeds for the most typical reading.
Enter both measurements to continue.
A schematic fit diagram, scaled to your cup size.
Measuring around fluctuation
The formula is unchanged — band from the rounded underbust, cup from the bust-to-band gap. The complication during nursing is that the bust number itself can shift meaningfully across a single day, before and after a feed.
cup difference = round(bust, in) − band
Measuring at a consistent, mid-point time gives the most useful everyday number, even though it won't perfectly match the fullest or emptiest moments of the day.
What to look for
Nursing bra features that matter
Drop-cup design
A cup that unclips or drops for feeding while the band stays fastened is the defining feature of a nursing bra.
Stretch panels
Some give in the cup or band helps absorb daily fluctuation without needing a size change every few days.
Wider band, secure fastening
A supportive band matters even more during nursing, when weight can shift meaningfully through the day.
Soft, breathable fabric
Softer materials next to the skin help with the sensitivity that often comes with breastfeeding.
Questions
Nursing sizing FAQs
Many people find a mid-point time — not right after a feed, not right before the next one — gives the most representative reading.
The band should still be snug and level; extra room is better handled through a stretch panel or drop-cup design than through a loose fit overall.
A cup that unclips or drops down for feeding access, while the band stays fastened — the main feature that distinguishes nursing bras from regular ones.
It can shift in the early weeks as supply regulates, then often stabilizes — re-measuring a few weeks in and again a few months later is reasonable.
Yes — this tool covers clothing sizing only. Pain, engorgement, or feeding concerns are best discussed with a doctor, midwife, or lactation consultant.
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