Breast Pump Flange Size Guide: How to Measure & Fit
🔑 Quick Flange Sizing Guide
To find your flange size: Measure nipple diameter in mm → Add 1-2mm → That's your flange size. Example: 17mm nipple = try 19mm flange. The "standard" 24mm only fits ~30% of women. Wrong size = pain, low output, clogged ducts.
What is a Breast Pump Flange?
The flange (also called breast shield) is the cone-shaped piece that fits over your nipple and areola during pumping. It creates suction to extract milk.
Flanges come in different sizes measured in millimeters (mm), ranging from about 15mm to 36mm. The size refers to the inner diameter of the tunnel where your nipple goes.
💡 Did You Know?
The "standard" 24mm flange that comes with most pumps only fits about 30% of women properly. That means 70% of women need a different size!
Why Correct Flange Size Matters
Wrong Size Can Cause:
- ❌ Pain and discomfort during pumping
- ❌ Lower milk output - can reduce production
- ❌ Nipple damage - cracking, bleeding
- ❌ Clogged ducts and mastitis risk
- ❌ Incomplete emptying of breasts
- ❌ Shorter pumping journey - discomfort leads to giving up
Correct Size Provides:
- ✅ Comfortable pumping sessions
- ✅ Optimal milk output
- ✅ Complete breast emptying
- ✅ Maintains milk supply
- ✅ Healthy nipple tissue
How to Measure Your Flange Size
Step-by-Step Measurement
- Wait until after pumping or nursing - Nipples are often larger when engorged
- Measure your nipple diameter at the base (where it meets the areola) - NOT the areola
- Use millimeters (mm) - A ruler, measuring tape, or printable sizing tool
- Add 1-2mm to your measurement - This is your starting flange size
Measurement Example
| Nipple Diameter | Recommended Flange Size |
|---|---|
| 15mm | 17mm flange |
| 17mm | 19mm flange |
| 20mm | 21-22mm flange |
| 22mm | 24mm flange |
| 25mm | 27mm flange |
| 28mm | 30mm flange |
⚠️ Important Notes
- Nipple size can change over time (pregnancy, nursing, pumping)
- Each breast may need a different size
- Size may vary by pump brand
- Elasticity affects fit too - stretchy nipples may need smaller flanges
Signs Your Flange Size is Wrong
Signs Flange is TOO BIG
- Areola gets pulled into the tunnel
- Nipple moves around with lots of extra space
- Lower than expected output
- Discomfort or pulling sensation
- Breast doesn't feel fully emptied
Signs Flange is TOO SMALL
- Nipple rubs against sides of tunnel
- Nipple turns white during/after pumping
- Pain during pumping (beyond initial suction)
- Red marks or damage to nipple
- Clogged ducts
- Low output
Signs of CORRECT Fit
- ✅ Nipple moves freely in center of tunnel
- ✅ Small gap around nipple (1-2mm)
- ✅ Little to no areola pulled in
- ✅ Comfortable throughout pumping
- ✅ Good milk flow and output
- ✅ Nipple looks normal after pumping
Complete Flange Size Chart
| Nipple Diameter | Flange Size | Notes |
|---|---|---|
| Less than 13mm | 15mm | Very small, may need specialty brands |
| 13-14mm | 15-17mm | Small |
| 15-16mm | 17-19mm | Small-medium |
| 17-19mm | 19-21mm | Medium |
| 20-22mm | 21-24mm | Medium (standard often starts here) |
| 23-25mm | 24-27mm | Medium-large |
| 26-28mm | 27-30mm | Large |
| 29mm+ | 30-36mm | Extra large |
Flange Sizes by Popular Pump Brand
Spectra
- Comes with: 24mm and 28mm
- Available sizes: 15mm, 17mm, 19mm, 20mm, 21mm, 24mm, 28mm, 32mm
Medela
- Comes with: 24mm
- Available sizes: 21mm, 24mm, 27mm, 30mm, 36mm
Elvie
- Comes with: 24mm and 28mm
- Available sizes: 21mm, 24mm, 28mm
Willow
- Comes with: 24mm
- Available sizes: 15mm, 17mm, 19mm, 21mm, 24mm, 27mm
Momcozy
- Comes with: 24mm
- Available sizes: 17mm, 19mm, 21mm, 24mm, 27mm
Baby Buddha
- Comes with: 24mm and 27mm
- Available sizes: 15mm, 17mm, 19mm, 21mm, 24mm, 27mm
💡 Pro Tip
Third-party silicone inserts (like BeauGen, Pumpin' Pals, or Legendairy Milk) can help you achieve a better fit with your existing flanges at lower cost than buying all new sizes.
Flange Fitting Tips
General Tips
- Measure each breast - They're often different sizes
- Re-measure over time - Size can change with nursing/pumping
- Try multiple sizes - You may be between sizes
- Consider silicone inserts - More comfortable, better seal
- Use lubricant - Coconut oil or lanolin reduces friction
If You Can't Find Your Size
- Try silicone inserts to reduce flange size
- Look at specialty brands (Pumpin' Pals, Beaugen)
- Consider different pump brands with more size options
- Consult an IBCLC (lactation consultant) for personalized help
When to Re-Measure
- After milk comes in (first week)
- If pumping becomes uncomfortable
- If output decreases unexpectedly
- Every few months during your pumping journey
- If experiencing recurring clogs
Frequently Asked Questions
Can I use the same flange for both breasts?
Only if both breasts measure the same. Many women need different sizes for each breast. Pay attention to how each feels during pumping.
Why do my nipples swell during pumping?
Some swelling is normal due to increased blood flow. However, significant swelling, turning white, or pain indicates wrong flange size (usually too small or too much suction).
Does flange size affect milk supply?
Wrong flange size can indirectly affect supply by preventing complete breast emptying, causing discomfort that leads to shorter/less frequent sessions, and potentially causing damage that makes pumping painful.
Are silicone flanges better?
Many women find silicone flanges or inserts more comfortable than hard plastic. They can provide a better seal and cushion. Popular options include BeauGen, Pumpin' Pals, and Legendairy Milk silicone inserts.