The short answer
👍 Getting the ‘right’ flange size can make a big difference to your comfort and milk flow.
😟 But it can be confusing figuring out which flange size is ‘right’
📏 You could start by measuring your nipple with a ruler, or our handy ‘nipple-sizer’ printout
👩⚕️ Ask your lactation consultant for help, especially if you’re having pain or discomfort
Don't want to read on? Download the nipple ruler and flange-fit checklist by clicking on the image 👇🏽
What is a flange?
Most pumps come with different sized flanges, which are the cone-shaped parts that fit to your breast.
What is flange size?
When people talk about “flange size”, they are referring to the diameter of the tunnel that your nipple is sucked into.
What is the usual flange size?
Breast pumps tend to have a range of flange sizes from about 20 millimetres to 36 millimetres.
If you don’t specifically order a different flange size, you’ll probably receive their standard size when you get your pump, which is usually about 24/25mm. Some pump brands come with two standard sizes to save you the trouble of ordering more than one.
Here’s a table of all the flange sizes that are available for pump brands.
Please let us know if you can’t see your pump, or we’ve got it wrong, and we’ll get onto that ASAP.
Finding the correct size
It’s important to get the right flange size for you, so that you have the best possible comfort, seal and milk flow.
If your pump flange size is too big, you can pull your areola unnecessarily into the pump funnel and damage the skin and tissue. We know from this study, and this study, that about 15-17% of women who use breast pumps have nipple injury and damage.
If your pump flange size is too small, you can rub your nipple against the plastic or block milk duct openings.
👆🏼 This flange is too large. See how the areola is sucked in with the nipple and swells.
👆🏼 This flange is too small. See how the nipple rubs on the side of the tunnel, and can’t really move much.
👆🏼 This flange looks about right. See how the nipple extends within the tunnel, but the areola says mostly where it is.
Unfortunately, the only thing you can change with most breast pumps to suit your nipple is the diameter of the tunnel that your nipple is sucked into.
Pumps don’t really take into account your nipple shape (inverted, flatter, rounder, longer), or how your nipple responds to the pump suction – whether it is elastic (stretches a lot) or fibrous (doesn’t stretch much). We made Milkdrop cushions for this reason, but more on that later.
How do I know if my flange size is too small?
Some signs that might indicate that your flange is too small are:
your nipple doesn’t move easily in the tunnel of the flange
you have indents on the top or close to the side of the nipple
you have pain or rubbing of the nipple (not areola)
you feel like your ducts are blocked by the flange
it takes you ages to get milk flowing
your breasts still feel full after expressing
How do I know if my flange size is too large?
Some signs that might indicate that your flange is too large are:
your areola (the part around your nipple) is drawn into the flange
you have swelling and soreness of your areola and the base of your nipple when you take the pump off
you have chafed skin in a ring around your areola
you don’t have good suction - the pump falls off, loses contact with your breast when its on, or it makes suction-y squelchy noises
you have milk leaking from the pump between your breast and the flange
it takes you ages to get milk flowing
your breasts still feel full after expressing
How will I know if I have a proper flange fit?
When you have the right size for you, you should be able to check-off this list.
So, your nipple should move freely, without touching the sides. Your areola should move a tiny bit, but not be sucked into the tunnel with your nipple. You may feel tugging but not pain or discomfort. When you remove your breast after a session, your nipple might be extended but your areola shouldn't be bloated and sore. You should have a good seal, which means you won't have air around your nipple or hear any suction-y noises 🤭. You should get good milk flow (squirts or faster droplets of milk), and after pumping for a session, you should feel that you've drained as much milk as you can.
If you find yourself needing icepacks, or heatpacks when you’re finished, then check your flange size, and seek help from your lactation consultant or doctor.
How do I choose the right flange size for my nipple?
To choose the right flange size, the most common approach is to measure your nipple diameter and choose the closest flange available for your pump.
Scroll down for detailed instructions on how to measure your nipple.
Measuring can be confusing because your nipple is affected by whether you’ve just pumped (and your nipple is swollen) or not. Also, sometimes you are between sizes or your nipple is much smaller than what’s available.
If you’re having trouble measuring, but you have access to a few different flange sizes (perhaps your friendly lactation consultant or some friends who pump can help you here), then you can go by feel. Just try on different flanges, and work through the flange-fit checklist above.
Whichever method you try, remember that the flange size you choose is just a starting point. You may need to change it up as you get used to pumping or as your breast changes over time.
How do I measure my nipple?
Here are the steps to measuring your nipple. Much like cooking a recipe, you’ll have the most success if you read through the steps first (even though it’s boring).
Step 1. Get yourself some sort of measuring device.
You can use a ruler, some measuring tape from a sewing set or a special ruler designed especially to figure out nipple size, which you can download here.
👆🏼 If you use this fancy nipple ruler, you need to print (make sure your printer isn’t scaling the document in the settings) and cut out the semi-circles with scissors.
Step 2. Look at your nipple (we’re not kidding)
You need to figure out what you’re measuring exactly, before you start.
You want to measure the distance from one side of your nipple to the other. Your nipple is the pointy or bumpier part in the middle. Your areola is the wider circle or darker skin around it👇🏽
To measure, you will start from one side of your nipple where it meets the areola, and measure across to the other side. Take care not to measure the areola, because you’ll end up measuring too big.
👇🏽 Here’s what that might look like on your nipple.
Step 3. Prepare your nipple.
Some advice recommends that you measure after pumping, but that can be problematic for two reasons:
You have to have a pump handy, and be ready to use it (i.e. lactating right now)
If you’re pumping on a flange that’s too large already, your nipple will likely swell to the size of the flange and be bloated. This would mean that you’d measure too large.
We suggest that rather than pumping, just stimulate your nipple. You can do this by pulling on your nipple gently with your fingers, which will raise it or plump it up a bit.
Step 4. Measure your nipple
Measuring is often best done in front of a mirror, or with the help of your partner or carer.
Using the special nipple ruler:
Place the semi-circle cut-outs against your nipple, starting with the smallest one. Keep going up a size until your nipple comfortably pokes through. If you have inverted or flatter nipples, choose the size that fits around your nipple.
👆🏼 click this to download the nipple ruler.
Using a regular ruler or measuring tape:
If you’re rusty on reading millimetres and centimetres on a ruler, here’s a refresher.
👆🏼The little lines are millimetres (mm). Most rulers show a big line every 10mm, and a half line every 5mm. As for centimeters? Well, 10mm = 1cm!
👆🏼 When you’re measuring, you just need to count every line (the millimetres) from one side of the nipple to the other to figure out your nipple “size” or diameter. In this photo, the nipple measurement is 17mm.
Step 5. Do some math
Now you have your diameter, add 1-2mm and choose the closest flange size available from your pump brand. Use the table above, or google your pump for flange sizes.
You may run into issues here, especially if you measure on the smaller end. For example, if you measure 12mm, you can see that for most brands, then the closest size for you is….21mm.
Thankfully, there is help for you. The following companies make inserts or separate flanges that you can attach or insert in your pump that better match your size.
Step 6. Test and change it up
As with most things pumping, you may need to try out your new size, run through the flange-fit checklist, and then change if you need.
Common questions about flange sizing
What’s a ‘normal’ nipple size – am I doing this right?
The female body is beautifully diverse. To give you an idea, nipple size on one person might be 5mm and another might be 40mm. If you’re measuring numbers somewhere in that range, then you’re probably doing it right.
My nipples are measuring different sizes
It’s rare for people to have two nipples that are completely identical. Your nipples are sisters, not twins, and it is possible that you need different flange sizes for each breast.
What if I’m between sizes?
Many women measure between flange sizes or measure much smaller than the flange sizes available. For example, you may need an 18mm or 19mm flange, but the smallest flange your pump comes with is a 21mm. If this is you, don’t worry, there are still options!
You can order special flanges or inserts that are made to help with sizing. They aren’t manufactured by the same brands as your pump but are designed to be compatible. Make sure you check compatibility first before you order.
Remember that your nipple size changes over time. Milkdrop can help here, because it’s so soft, it stretches to your shape, so you reduce the chance of having to buy different sizes as you move through your feeding and pumping journey.
But my nipples don’t look like your diagram?
We’ve tried to show how a stylized nipple might look in a breast pump. There’s every chance that your nipple doesn’t look anything like the one we have presented. Some people have flatter or inverted nipples, others rounder, others pointier. Some people have elastic nipples, meaning that their nipple can stretch longer than about the 3x that is “typical”, and in their case, their nipple fills up whatever space is available.
Measuring is confusing me. Is there another way?
You don’t have to tell us that measuring your nipple is a bit absurd!
It can be confusing to figure out your dimensions, and when you do, you might be between sizes. Also, your nipple changes size when you pump, feed, and even with time since you had your baby.
If measuring is too much, then go by look and feel. Try a few different sizes and look for one that allows your nipple to move freely within the tunnel (not touching the sides), without your areola also being drawn up with it.
I’m not able to check everything off the flange-fit checklist
Ideally, once you get your flange size sorted, you can check off the flange-fit checklist. But even with the right flange size, you can still have trouble with comfort, seal and milk flow. Speak with your lactation consultant. Or give Milkdrop cushions a try! We made them super squishy so they mold to the shape of your breast providing comfort and a better seal.
Can I measure when I’m pregnant, and use that flange?
Sort of. Sorry, it’s not an easier answer.
You can make a start, and choose a flange, but remember that your nipples change, especially as your body starts to move from creating colostrum, to creating mature milk. You may be fine, just run through the checklist to be sure when you do start pumping. If you need a different flange size then, you can usually order them fairly easily.
Top 3 mistakes when choosing a flange size
Here are the most common mistakes we see that you want to avoid:
1. Measuring your areola, rather than your nipple.
Your nipple is the centre part, your areola is the darker, bigger circle around your nipple. The flange should fit so that your nipple is free to move in and out, but your areola isn’t also sucked in.
2. Using the standard flange size that comes with your pump.
The standard size you receive when you first purchase a pump is usually 24/25mm. You might be lucky, and find that this is the correct size for you. But based on our research at Milkdrop, nipple size ranges from 5mm to 40mm. Changing up that flange size to suit you can make all the difference to your comfort, seal and milk flow.
3. Putting up with pain or discomfort.
Women are great at putting up with pain. We’ve done it since we first started menstruating. Many of us did it during pregnancy, and again during labor/surgery and recovery. BUT, pain and discomfort from breast pumping is not necessary. Taking care of your breasts and nipples is vital to being able to feed breastmilk to your baby. This is not the time to put up with discomfort, gurrl.