Flange sizing

The flange is the funnel that fits over your nipple. A flange that fits well feels comfortable and lets milk flow. One that's the wrong size can hurt and damage the nipple and breast. Nipples vary, and left and right can need different sizes.

Why size matters

• Pumps can injure the nipple and breast when the flange is the wrong size, the suction is too high, or sessions run very long.
• You can often get different funnel sizes to fit your nipples.

Finding your size

1. Measure the width of each nipple tip in millimeters before pumping, using a ruler marked in millimeters.
2. Try two or three sizes on a low suction setting: one a little smaller than the nipple, one about the same, and one a little bigger.
3. Keep the size that's comfortable and gets milk flowing easily.

Pump makers publish their own sizing charts. The health bodies cited here give no single formula, and research on sizing is still early, so comfort and milk flow are the best guide.

Signs of a good fit

• Your nipple sits in the center of the tunnel and moves a little back and forth.
• Only a small amount of breast tissue enters the funnel.
• Pumping feels comfortable from start to finish, and your nipple is about the same width afterward.

Sources differ on whether the nipple can touch the tunnel walls. One NHS leaflet says it shouldn't rub (NHS Guy's and St Thomas'), and another says the sides can touch lightly while it glides (NHS Southampton). Both agree that rubbing that hurts means a change.

Too small or too big

Compare sizes in Chickpea

Save each flange size as its own setup and pick it when you log a pump session. Once each size has enough sessions, Insights shows which one gets more milk, or that they're about the same.

When to get help

• Pain or cracked skin that doesn't ease after changing size: a lactation consultant (IBCLC) can watch a session and help with fit.
• A red, hot or hard area, or feeling feverish and unwell: call your doctor or midwife.