One of the most important things when pumping breast milk is making sure that you have the best flange fit so that pumping isn’t painful. Here’s everything you need to know about breast shield sizing.
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What is a breast shield?
Breast shields (also called “flanges” or “horns”) are the part of the pump that fits around your breasts.
When the pump is set up and turned on, your nipple is sucked into the flange tunnel, pulling the milk out.
Standard size breast shields (often 24mm) will come with your breast pump. However, many people need a different size – below is an unscientific Instagram poll I recently did.
How are they sized?
Breast shields are sized based on the diameter of your nipple in millimeters.
This means that it’s possible to have large breasts, but still need a small breast shield size. Sizing is based on nipple size, not breast size.
Why is using the correct breast shield size important?
Using the incorrect breast shield size can cause three major problems – pain while pumping and damaged nipples, decreased milk output, and clogged milk ducts.
(You don’t want any of these, which is why it’s a really good idea to make sure you have the right size!)
How does pumping with the wrong size cause pain?
- If your breast shield is too small, your nipple won’t be able to move freely in the flange tunnel, which can cause nipple pain because the fit is too tight.
- If your breast shield is too large, too much of the tissue around your nipple gets pulled into the tunnel. The agitation related to areola getting pulled in where it shouldn’t can bruise that tissue and cause pain and inflammation.
How does it result in decreased milk output and clogged ducts?
Pain inhibits letdown, so if pumping hurts, it will be harder for you to get your milk to letdown.
Additionally, if there is pressure from your flanges where it shouldn’t be, this can cause the ducts to flatten or constrict the flow of milk.
And if milk isn’t being removed effectively because your flange size is not correct, you may be more susceptible to clogged milk ducts.
What are some signs that your flanges don’t fit correctly?
Here are a few reasons to consider using a different breast shield size:
- You’re having pain when you pump.
- Your nipple can’t move freely in the tunnel and turns red.
- More than a little areola is pulled into the breast shield.
- Your breasts don’t feel empty after 15-20 minutes of pumping.
- Your nipples stretch far into the flange, almost to the end of the connector.
What sizes are available?
Different breast pump manufacturers sell different breast shield size options. Here are a few examples:
- Spectra: 16mm, 20mm, 24mm, 28mm, and 32mm
- Medela: 21mm, 24mm, 27mm, 30mm
- Motif: 16mm, 19mm, 21mm, 24mm, 28mm, and 32mm
Additionally, there are several companies such as Nenesupply and Maymom that make aftermarket breast pump replacement parts, and these may include additional sizes. For example, Nenesupply sells the same sizes as listed above for Spectra, but they also sell 21mm breast shields, if you need something slightly larger than 20mm.
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How do you find the correct breast shield size?
So what should you do if you think you might have the wrong breast shield size? You have a few options to for breast shield sizing.
1. Measure with a ruler
You can download a printable breast shield size ruler and use that to measure your nipple size.
Below is an example of what these rulers look like. You cut out each of the circles, and then see which circle best fits your nipple after you finish pumping.
Legendairy Milk sells a ruler for flange sizing that you can use to measure your breast shield size – use 15EPUMP for 15% off.
2. Get sized
You can also ask a lactation practitioner to size you for flanges.
You may be able to find someone local to you who can help you in person. When making the appointment, I would be clear that you’re asking about pumping so that you know they will be able to help you.
Some services also help you get sized virtually via photos and video.
3. Try several different sizes
Another option, if you don’t want to measure/are finding it confusing or if you are still having pain with the size that you measured for, is buying and trying several different sizes.
One way to do this is to buy one size up and one size down from what you measured for or what you’re using now, and see what feels best.
The upside is that you can be sure the size you’re using is best for you compared to other options. The downside is obviously that you might end up buying a lot of sets of breast shields that don’t fit, and that adds up.
Is it possible for each side to need a different size breast shield?
Yes. It’s possible to have nipples that are two different sizes; some amount of asymmetry between breasts is normal. (Just like it’s possible – even common – have lopsided breast milk output from your breasts.)
It’s a good idea to measure both sides to ensure each side has the correct size.
If you need different sizes, just buy one of each size, and then you have two sets of breast shields that will fit you perfectly.
Can your breast shield size change over time?
Yes. Therefore, if you start feeling discomfort when pumping, it’s good idea to measure yourself or try a different size even if you were sized before.
What if you can’t find a size that fits you?
Sometimes folks try a ton of different breast shields and can’t find one that works. This can happen for a few reasons.
In between sizes
If you are in between sizes, BeauGen cushions are a good option, as they will reduce your flange size by about 2mm.
So for example, if you measure yourself at 26mm and have a Spectra breast pump, you could try using 28mm flanges with cushions.
Beaugen cushions are available on amazon or buying directly from BeauGen.
Elastic nipples
Another cause for this can be elastic nipples. With elastic nipples, the nipple stretches to fit whatever size breast shield is being used – sometimes reaching to the end of the tunnel.
Usually, with elastic nipples, you will want to try breast shields that are a different shape and material (silicone), such as Pumpin Pals or LacTeck BabyMotion flanges. These (along with BeauGen cushions) can sometimes help keep your nipples from stretching out.
You can use the code EPUMP10 for 10% off LacTeck BabyMotion flanges.
More on alternate breast shields options here.
Have you struggled with breast shield sizing? Feel free to ask any questions about flange fit in the comments!
Comments & Chitchat
i been exclusive pumping and trying to latch for almost 7 months. i think i am experiencing vasospasms as well. i have a spectra and a lansinoh. i am pumping and my milk wont come out. maybe it is the flange i believe. ive tried flanges from 19 to 21. i dont want to give up. i need more help please
Hi Cassandra! I’m so sorry to hear that! Have you tried measuring or getting virtually sized? This is an option if you think it might help?
https://www.legendairymilk.com/collections/pumping-accessories/products/silicone-nipple-ruler
I have had a lot of struggle with my first two and am very worried with a third on the way. I feel like I have a unique case and have not been able to get help from anywhere.
My right breast has a very severely inverted nipple. However, i think my nipple itself is very long so when pumping I had to set it to the highest suction to get milk into the bottle. I don’t know if this makes sense, but it felt like the milk was draining back into my breast at lower settings or I didn’t get any milk at all. However, the high setting caused me a lot of pain and bleeding all the time. The other issue is that I cannot get the right flange. This is because the base of my nipple is fairly small, but when the nipple is fully drawn out, the tip is quite large. I think the term is pedunculated? However, since the nipple is inverted and only draws out during the high setting pumping, it’s hard to explain a lactation consultant. Once drawn out at high setting it rubs against the flange and cause significant pain.
Please advise on what brand/type I can try this time as I am very nervous about pumping from the right side. Thank you!
Hi! First, congrats on your pregnancy! I am going to be honest – I have not heard of this before. What I think I would try is a silicone flange (or a breast insert) that will grip the nipple a little better so that it’s not pulling so far in, and so that you don’t have to use that high setting. I don’t know if that will help but I think it’s worth a shot. The things I would try are Beaugen inserts, LacTeck flanges, or silicone pumpin pals.
I really hope this helps! Good luck!
Hello and thank you again for your beautiful site. It was such a relief to have during 2020 with our first whom I exclusively pumped for 11 months. I could not have done it without the wealth of info, resources, and community. I often refer people to this site who are nursing/pumping because it was so helpful to me. Thank you again.
Thankful to find flange sizes were wrong then and able to use 19-22mm.
Here I am with my second baby 3 months post partum and wondering if flange sizes are wrong. We do a mix of nursing and pumping which is a whole new ball game. My sizes must have drastically changed unless husband and I measured wrong? Thought I was 19-21mm (one side slightly larger) but I also have elastic nipples. Ve noticed pain and discomfort while pumping eveb after trying some stricks. Measuring after pumping tonight and I’m measuring 12-13mm… Is that possible? If so, I can get the maymom inserts happily but curious if the change and size is normal or even exists? I’ve noticed my supply has gone down despite power pumping, hydration, and what not so it must be fit. Help please. Thanks.
Hi Kathy! Congrats on baby #2! I’m so happy for you!
Ugh I’m so sorry! It is possible for flange sizes to change. Are you using silicone flanges b/c of elastic nipples? One idea – have you looked into getting virtually sized? A lot of people do it for $25 or less?
Thanks for this article. If I’m in between sizes (21 and 23 mm), do you recommend sizing up or down? I keep getting clogged ducts on the side that’s in between sizes and I’m currently using a 21mm so I’m wondering if I should try sizing up and if that would make a difference. I don’t really have pain currently.
Hi Marissa! In this case, I would get one of each size and just test out which ones feels better/gives you better results. It’s more of an art than a science when it’s that close. Good luck!
This is me second time breastfeeding my daughter is now 4 months but I was not pumping as much as felt I should and realize now that my flanges are too big cause too much is getting sucked into the flanges! I am ordering some smaller ones THANK YOU!
Thanks for sharing this. I love your blog and have learned a lot of good info. I’m about six weeks PP and have been exclusively pumping since the start. When I pump two things hurt:
1. The rim of the shield .. feels like it bruising the skin and the whole shield feels too big but even if you change sizes, the diameter of the shield doesn’t change. Not sure what to do here?
2. When I go from massage to express- the first initial five seconds feels really painful but then subsides and I’m able to go up a few levels over the course of my pump session which then leads to more milk. Higher expression level- the more my Milne comes out.. but I can only stand a certain level for too long.. is this normal?
Hi Morgan! Congrats on your sweet newborn! I’m wondering if maybe a silicone breast shield would be more comfortable because it’s softer?
Do you think the pain is painful letdown OR related to the change in suction from the pump?
Hi Amanda, should I be measuring the nipple before or after I pump? Also, my nipples are slightly oblong so would I take the longest width across? It’s sort of annoying because I can see that the flange doesn’t have a good seal on the breast where it is furthest from the nipple, if that makes sense.
Hi Sharon! I would measure after you pump, and I would take the longest width across. But definitely look into getting sized if you’re unsure – Milky Mama does virtual sizing for $5 and pump_momma_pump does it for $25. Hope that helps!
Hi Amanda!
I found your page too late (almost two months struggling with a breast pump, wrong size of flanges, little milk coming, nipple pain…) but I’m happy for all those articles!
I have still nipple pain, even now i found the right size (I have them all, 15, 17, 19, 21, 24 & 27…), I’m somewhere around 17. It still hurts during (or I have to put very very little vacuum which doesn’t empty my breasts) and after and actually all the time. Nothing above helps.
The nipples go quite far into the flange, or if smaller, they scrub. No size is optimum. Or I dont know what it should look like during the pumping…
I’m trying to get enough milk because if I do, then we can start breastfeeding because my baby starts to suck quite well (now it’s more 15-50ml of both sides per session).
The pump seems to get milk out quite well (only a few drops when I do hand extraction at the end ),but as I said, it hurts.
If you have an idea it may help!
Btw, having my laptop nearby changed my sessions, doing finally what I want during this “lost” time.
Thanks very much!
Hi Nessie! It kind of sounds like you may have elastic nipples? Does this sound familiar at all?
https://exclusivepumping.com/how-to-make-pumping-with-elastic-nipples-less-painful/
Yes exactly! I’ve found about elastic nipples while searching for how it should look like when pumping, and your article completes it very well. Already using coconut oil reduced the pain almost to nothing. Why don’t they suggest this at the maternity when you’re constantly referring to a huge pain?? I will see if I find the pumpinpals in France, it looks like a good product.
Thanks for your reactivity, it really helped me a lot (still regretting that I haven’t found this page right at the birth…)!
I’m wondering when should I measure my nipples? Will they change size after the birth once my milk comes in? I’m almost 28 weeks and will be able to order my pump through insurance next week. I’m EPing from birth, so I’m excited to get my pump early to figure out how to use it. But I also want to have extra pump parts, especially extra sets of flanges, ready to go from the start too, to make the whole process easier on myself. But is it too early to measure to buy extra flanges now, when I’m just entering my third trimester? Do I have to wait until my milk comes in? Will my nipples change size once the baby is born? I’d really prefer not to waste money (or parts) by buying lots of different sizes, so I need to know if I should wait to measure or if I can go ahead and measure and purchase extra parts now. I can’t find any information to answer this question, so I’m really hoping you can give me some guidance. Thank you!
Hi Julie! Congrats on your pregnancy! I know this isn’t what you want to hear, but I would wait to buy extra flanges until you measure or get sized after birth. You can get all the OTHER parts now, but just might want to hold off on flanges. That way your extra washing is just one piece. I’m sorry I wish I had better news!
OMG! The struggle has been exhausting and expensive. I’ve tried all the solutions you mentioned above and the best I can find is the babu motion flange in 18mm. This is bruising though and pumping 140mins /day is taking its toll. Do you anyone who just makes a plain silicone flange?
Nobody that im aware of. Silicone inserts go change flange sizing yes. Maymom does as does freemie for their specific cups. But depending on your pump some have silicone cushions that go in the flanges. And legendairy milk cups come with silicone flanges but they only work for the cups and for elvie pumps.