What is a breast pump flange?

The breast pump flange size is a funnel-shaped piece of plastic that fits over your nipple. It forms a vacuum seal around your areola and then draws your nipple into its funnel to extract milk. Most pumps come with a standard 24-millimeter (mm) flange. But they’re available in a wide range of sizes, generally anywhere from 21 to 36 mm. The size indicates the diameter of the small tube on the flange's narrow edge. You can find different-sized flanges through your pump manufacturer, sites like Amazon, or any baby supply store.

The right flange fit will help you express as much breast milk as efficiently as possible. Your flange size generally depends on your breast tissue and skin elasticity. If your flange is too tight, it will constrict your breasts, which can cause clogged milk ducts that don’t release milk as quickly. But if your flange is too loose, you won’t remove all the milk from your breast, which can lower your milk production. It can also cause unnecessary nipple pain and even injury to your nipple. If pumping hurts, it can impede your milk supply. You’re also less likely to stick with it.

To measure your nipple diameter (its width), you'll need a ruler or a measuring tape. You can also estimate with coins: A dime is approximately 18 mm, a penny is 19 mm, a nickel is 21 mm and a quarter is 24 mm. Before you measure, stimulate your nipple, either by rolling it between your thumb and finger or applying ice to it, to make sure you have its full size. Focus on its diameter at the base, and don’t include the areola. Remember to measure both of your nipples as they can be different sizes.

Flanges vary from company to company, so you may want to try a few out. You might find that another brand’s flanges work better with your body. It can take some time to find the ideal gear, but most pump and flange combos are totally fine. Remember also that your nipple size (and hence your flange size) may fluctuate throughout your breastfeeding journey.