Flange Size Guide: How to Measure at Home for Your Breast Pump
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The quick answer: Your flange size is the width of the tunnel your nipple sits in, measured in millimetres. To find it, measure the width of your nipple (not the areola) at its base, then check your pump brand's size chart. Most charts add about 2 to 4 mm to your nipple measurement. Always go by your own pump's guide, because brands differ.
A flange that fits well makes pumping more comfortable and helps you empty the breast better. A poor fit is one of the most common reasons pumping hurts or gives less milk.
What Is a Flange?
The flange, also called a breast shield, is the funnel-shaped cup that goes over your nipple and breast. Your nipple is drawn into its tunnel when the pump runs. If the tunnel is too tight or too wide, you'll feel it.
How to Measure Your Nipple at Home (3 Steps)
- Get a soft tape or a small ruler in millimetres. A paper ruler or a printed measuring guide works too. A soft tailor's tape is easiest.
- Measure across the widest part of your nipple, at its base. Don't include the areola, the darker skin around it. Measure when the nipple is in its natural, slightly erect state. Many people measure after pumping, because that's the size the nipple reaches during a session.
- Check your pump's size chart. Take your measurement in millimetres, add the amount your brand recommends (often 2 to 4 mm), and pick the closest flange. Measure both sides. They can be different.
Example: If your nipple measures 16 mm, a brand that adds 3 mm would suggest a flange of about 19 mm. Another brand may differ, which is why the pump's own chart matters.
How to Tell If the Fit Is Right
| What you notice | What it may mean |
|---|---|
| Nipple moves freely, little areola is pulled in, no pain | Good fit |
| Nipple rubs the tunnel wall, looks pinched or white after pumping | Flange may be too small |
| A lot of areola is pulled into the tunnel, the breast feels sore or swollen | Flange may be too big |
| You get very little milk even though you feel full | Fit or suction may need adjusting |
| Pumping hurts, even at a low level | Stop, check the fit and ask for help |
Quick Fit Check During a Pumping Session
- Centre your nipple in the tunnel before you switch the pump on.
- Start at the lowest level, in massage mode if your pump has one.
- Look at your nipple while it pumps. It should move in and out without rubbing the sides.
- Increase suction only while it stays comfortable.
Things to Remember
- Your size can change. It can shift in the first weeks after birth and again over time. Re-check every few weeks, and if pumping starts to feel different.
- Each side can be different. Measure left and right separately.
- Sizes aren't the same across brands. A 24 mm flange from one brand may feel different from another.
- Inserts can help. Some pumps offer silicone inserts to reduce the tunnel size. Check what your pump's manual says.
For more on pain and how to fix it, read Does breast pumping hurt? If your output is low, see Not getting much milk when pumping?
Choosing a Pump With Good Flange Options
Before you buy, check whether the pump brand shares its flange sizes and whether you can get other sizes later. Our guide on single vs double breast pumps lists what else to check. Everything about pumping is collected in our Breast Pumping Guide, and you can see NestFlow here. If you aren't sure about a fit, WhatsApp us and we'll help you check it.
Questions Moms Ask Us
How do I know my flange size?
Measure the width of your nipple at its base in millimetres, then check your pump brand's size chart. Most charts add about 2 to 4 mm.
Do I measure the nipple or the areola?
The nipple only, not the areola.
Can I have different flange sizes on each side?
Yes. It's common for the two sides to differ, so measure each one.
Can a wrong flange size reduce milk?
It can reduce how well the breast empties and make pumping uncomfortable. A better fit often helps. If supply worries you, talk to a lactation consultant.
Should pumping feel painful at first?
It can feel unfamiliar, but it shouldn't hurt. If it does, stop and check the fit and suction.
How often should I re-measure?
Every few weeks, and any time pumping starts to feel different.
Is there a printable flange chart?
Use a ruler in millimetres, or the printable guide that comes with your pump or from its brand's website. Each brand's chart is a little different.
The Bottom Line
Measure, match to your pump's chart, and trust how it feels. A comfortable pump is one you'll actually use. If pain or low milk continues, please see a lactation consultant.
General information, not medical advice. Please talk to your doctor or a lactation consultant about your own situation.
We get it, mumma. Nestush gets it.