Flange Size Calculator
Find the recommended breast pump flange size from your measured nipple diameter, plus the nearest common standard flange size.
Why flange size matters
A breast pump flange (breast shield) that fits properly should let the nipple move freely in the tunnel without excessive areola tissue being pulled in, and without rubbing or pain. A poorly-fitted flange can reduce milk output and cause discomfort.
How this calculator works
Measure the diameter of your nipple (not the areola) at its base, in millimeters, ideally right before or during a pumping session. General fitting guidance recommends a flange diameter about 2-4 mm larger than your nipple diameter to allow comfortable movement. This calculator adds that margin and matches the result to the nearest common standard flange size sold by most pump brands.
This tool provides general educational guidance only. Comfort and fit can change over time and differ between breasts; if you experience pain, reduced output, or nipple damage, consult a lactation consultant for a professional fitting.