Know Your Breast Pump Flange Size

How to Know Your Correct Flange Size (Step-by-Step Guide)

What is a flange size?

The flange is the funnel part of your breast pump. The size refers to the diameter of the tunnel opening (in mm) where your nipple goes in.

Correct flange size helps:

• Better milk output

• Less pain and nipple damage

• More comfortable pumping sessions

STEP 1: Measure your nipple (BEFORE pumping or latching)

This is the most important step.

Measure only the nipple, not the areola (brown part).

Best time:

• Before pumping or breastfeeding, or

• At least 30 minutes after your last session

  
  

  Ways to Measure Your Nipple

  
  

  

  
  

Option A: Using a Ruler (mm)

• Use a ruler with millimeter (mm) markings

• Stand in front of a mirror

• Measure straight across the widest part of the nipple

• Do NOT include the areola

Write down the measurement in mm

Option B: Using a Nipple Ruler / Size Guide

• Place the nipple into the circle holes

• The hole that fits snugly without squeezing is your nipple size

• Make sure only the nipple fits, not the areola

Note the size in mm

STEP 2: Add allowance (very important)

After measuring, add 1–3 mm to get your flange size.

Formula:Nipple size + 1–3 mm = Flange size

Example:

• Nipple measures 16 mm

• Add 2 mm

• Suggested flange size: 18 mm

STEP 3: Choose the nearest available size

Common flange sizes: 17 mm, 19 mm, 21 mm, 24 mm, 27 mm

If you’re in between:

• Sensitive nipples / swelling easily → choose the smaller

• Feeling pinching or rubbing → choose the bigger

STEP 4: Pump & do a FIT CHECK (after pumping)

After pumping is for checking fit — not for measuring size

✅ Correct flange fit looks like:

• Nipple moves freely in the tunnel

• Minimal areola pulled in

• No rubbing on tunnel walls

• No pain (gentle pulling is normal)

• Nipple stays round after pumping

• Good milk flow

❌ Too SMALL if you notice:

• Rubbing or pinching

• Lipstick-shaped nipple

• Redness, blisters, cracks

• Low output despite strong suction

❌ Too BIG if you notice:

STEP 5: Re-measure When Needed

 Your flange size may change over time, especially during the early postpartum weeks, on engorgement days, if pumping becomes painful again, or if your milk output suddenly drops. Re-measure anytime your comfort changes. In our shop (Flange Insert), available flange inserts are 13 mm, 15 mm, 17 mm, 19 mm, and 21 mm. If you need more help choosing the right size, feel free to message us at babeeboo.ph@gmail.com 💗