Breast Pump Sizing Kit: Find Your Correct Flange Size

By Smarter technology for women | Elvie Trainer and Elvie Pump ... | Published: 2026-10-21

Category: How-to Guides

Learn how to use a breast pump sizing kit to measure your flange size for comfortable, efficient pumping. Step-by-step guide with common mistakes to avoid.

Quick Answer

Use a breast pump sizing kit with inserts ranging from 15mm to 30mm to measure your nipple diameter and find the flange that fits snugly without rubbing.

Why Flange Fit Matters

A poorly fitted flange can reduce milk output, cause discomfort, and lead to nipple damage. The right size ensures the nipple is centered and moves freely without the areola being pulled in.

Most pumps come with a standard 24mm or 28mm flange, but many people need a smaller or larger size. A sizing kit lets you try multiple sizes before committing.

What the Sizing Kit Includes

The Breast Pump Sizing Kit from Elvie includes a range of insert sizes (15mm to 30mm) designed to fit standard flanges. Each insert is marked for easy identification.

Using the kit helps you find your perfect fit without buying multiple separate flanges.

Step-by-Step Flange Sizing Process

Measure Your Nipple Diameter: Use a ruler or the measuring guide included in the kit. Measure the base of your nipple (not the areola) while your breast is at rest. Record the measurement in millimeters. Common mistake: measuring the areola instead of the nipple. The flange should only fit the nipple.
Select the First Insert Size: Choose an insert that is 2–4mm larger than your nipple diameter. For example, if your nipple measures 17mm, start with a 19mm or 20mm insert. Checkpoint: if the insert feels too tight or causes pinching, go up one size.
Test the Fit with Your Pump: Place the insert into the flange, attach to your pump, and start a session at low suction. Observe if your nipple moves freely without rubbing the sides. The areola should not be pulled into the tunnel. Common mistake: using suction that is too high during the test. Start low and increase only if comfortable.
Adjust as Needed: If you feel discomfort or see redness after pumping, try the next size up or down. Repeat the test until you find a size that feels comfortable and produces good milk flow. Checkpoint: your nipple may change size during a session; choose the size that works for the majority of the pump time.
Confirm with a Full Session: Once you think you have the right size, pump for a full session (10–15 minutes). If you experience no pain and your nipple returns to its normal shape afterward, you have found your correct size.

Product Facts

Breast Pump Sizing Kit: Find your perfect breast pump flange fit with a wide range of inserts designed for maximum pumping comfort and milk output. Using the correct insert size prevents nipple rubbing and ensures efficient milk expression, making pumping sessions more comfortable and productive.
Breast Pump Sizing Kit