If you're using a breast pump and wondering why things feel a bit... off, the answer might lie in one simple detail: your breast shield size.
Many mums don’t realise that a poorly fitting breast shield can make pumping uncomfortable, less effective, and even impact your milk supply. If you’re finding pumping painful, frustrating, or just not effective, there’s a good chance the issue lies in the shield or flange size. The good news? With the right fit, pumping can become more efficient and comfortable, dare we say, enjoyable?
Here’s your no-stress, no-judgement guide to choosing the right breast shield size. Let’s take the guesswork out of pumping.
🍼 Wait, What’s the Difference Between a Shield and a Flange?
At The Night Owl, we break it down like this:
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Shield (aka breast shield): This is the soft silicone shield that sits against your breast. We offer two sizes: 24mm and 27mm.
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Flange insert: A soft silicone piece that sits inside the 24mm shield to reduce the tunnel size. We stock a range of flange inserts (from 13mm to 21mm) to match your nipple size more closely.
Think of the shield as the outer framework, and the flange insert as the internal fit adjuster, kind of like choosing the right shoe and then adding an orthotic.
⚠️ Note: Our flange inserts are only compatible with the 24mm shield, not the 27mm.
📏 How to Measure Your Nipple Size (It’s Easy, Promise)
To get the right flange fit, you need to measure your nipple, not your breast or bra size. This helps determine what flange insert (if any) you need.
Here’s how:
- Gently roll or stimulate your nipple so it's firm.
- Measure across the base of the nipple (just the nipple, not the areola) in millimetres (mm).
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Add 2-3mm to that number, that’s your ideal flange size.
***For example, if your nipple measures 17mm across, a 19mm flange insert would likely be your best fit, BUT it can take trial and error to see what works best for you.
If you're between sizes or have one nipple bigger than the other (completely normal!), choose different insert sizes for each breast. That’s the beauty of using a wearable breast pump from The Night Owl, you can customise each side.
🔍 Not Sure If You’ve Got the Right Fit?
Let’s decode the signs.
Your flange insert may be too small if:
- Your nipple rubs or blanches (goes white) in the tunnel
- It feels pinchy or sharp
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You’re not getting much milk despite a letdown
Your flange insert may be too big if:
- Your areola is getting pulled deep into the tunnel
- You see swelling or redness
- Your output is lower than usual
- It feels like the pump is working too hard, but not much is happening
✅ Signs You’ve Nailed the Fit
- Your nipple moves freely in the tunnel without rubbing
- Only a small portion of the areola is drawn in
- Milk flows well, and you feel comfortable
- You don’t dread your next session
Comfort + output = success.
What if You’re Still Not Sure?
You’re not alone, many mums find flange fitting confusing at first.
If you’re stuck between two sizes, we recommend:
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Trying both sizes (some mums find one size works better at different times of day or on different breasts)
- Reaching out to a lactation consultant for a personalised fit check
Picking Between the 24mm and 27mm Shield
Here’s where many mums get confused, because if your nipple size is smaller than 24mm, you’ll want to use a flange insert inside the 24mm shield.
- Choose the 24mm shield if your nipple is under 24mm and you plan to use a flange insert.
- Choose the 27mm shield only if your nipple is larger than 26mm.
Most mums fall between 13mm and 21mm, which means the 24mm shield + flange insert combo is the best fit.
Don’t Power Through Pumping Pain
A poorly fitted flange can make pumping harder than it needs to be and honestly, mums have enough going on. Getting the right shield and flange combo can help protect your supply, reduce discomfort, and make expressing feel less like a chore and more like a win.
✨ Whether you’re prepping to return to work, building a stash, or exclusively pumping, a proper fit is your secret weapon.