Breast Pump Flange Size Calculator

Your details

Measure across the base of your nipple at its widest point, not including the areola. Measure after gentle stimulation for accuracy.
mm
Cleveland Clinic advises adding 2 to 4 mm; Medela's own fitting guide says add 4 mm. There is no evidence-based formula, so +3 mm is used here as the middle of the accepted range. Try +2 mm if the areola gets pulled in, or +4 mm if the nipple feels restricted.
Elastic nipples can expand significantly inside the tunnel and may need a tighter starting size; flat or inverted nipples may need a slightly larger opening.
Recommended flange sizeStandard flange range
22mm

The flange diameter to try first

Size range to try21 mm to 23 mm
Nipple diameter (mm)19mm
Fit noteStandard nipple shape: start with the recommended size and assess fit after 2-3 pumping sessions.
22 mm
XS<17Small17-22Standard22-26Large26-30XL30+

Start with a 22 mm flange (range: 21 mm to 23 mm).

  • Your nipple measures about 19.0 mm across the base. With 3 mm of clearance, the starting flange size is 22 mm.
  • Try sizes in the 21 mm to 23 mm range if the first fit is uncomfortable. Most pumping difficulties resolve with a 1-2 mm size change.
  • A correct fit means the nipple moves freely with 1-3 mm of clearance on each side, no more than 2-3 mm of areola enters the tunnel, and pumping is comfortable.

Next stepAfter your first session, check for the signs of correct fit listed below. If you see rubbing, discoloration, or pain, adjust by 1-2 mm and reassess.

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