How to choose a flange size 

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Flange basics

What is a breast pump flange? 

Most pumps come with different sized flanges, which are the cone-shaped parts that fit to your breast. When people talk about “flange size”, they are referring to the diameter of the tunnel that your nipple is sucked into.

Why is it important to get the right size flange for my breast pump?

The right flange size will give you the best possible comfort, seal, suction 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. About 15% 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.

[gif of too large]

[gif of too small]

[gif of just right]

Unfortunately, the only variable you can change with most breast pumps 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.

 

Flange sizing

Which size flange do I need?

You will need the flange size that best matches your nipple.

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 24mm. Rather than provide the whole flange, some pumps provide an insert that you can place in the existing flange that brings the size down a bit. 

You can see all the flange sizes that are available for most pump types below. Please let us know if we haven’t listed your pump, or we’ve got it wrong, and we’ll get onto that ASAP.

 

How do I figure out the correct flange size for me?

There are a few ways to figure out which flange size to use:

  • Measure your nipple. Figure out your nipple diameter, add a few millimetres (mm) and choose the closest flange size available.
  • Go by look. Place different flange sizes on your breast and choose the one that doesn’t suck in too much areola (too large) and doesn’t jam against your nipple (too small).
  • Go by function. Try on different flange sizes and choose the one which collects the most milk (and is comfy).

Neither of these options is without its flaws.

Measuring nipples is confusing, because your nipple measurement can be affected by whether you’ve just pumped (and your nipple is swollen) or fed or not. Going by look means you need to have a pump and lots of flange sizes on hand already. And going by function is tricky because milk volume fluctuates so much between and during pumping sessions (more on that here), and it’s hard to know if it was your flange size or something else that made the difference.

Whichever you try, and you may try all three, we’ll explain each in detail below.

Remember, the flange size you choose is just a starting point. You can (and may need to) change it up as you get used to pumping or as your breast changes over time.

 

Measuring your nipples

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 the 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. Prepare your nipple.

Some advice recommends that you do this after pumping, but that can be problematic for two reasons:

  1. You have to have a pump handy, and be ready to use it (i.e. lactating right now)
  2. 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 it a bit with your fingers, which will raise it or plump it up a bit.

Step 3. Figure out what you’re measuring exactly. 

You need to measure the diameter, or the distance across your nipple, from the base of the nipple where it meets the areola. Take care not to measure the areola, because you’ll end up measuring too big. 

[diagram of a nipple, and where it should be measured]

 

Here’s what that might look like on your nipple.

[image of a few real nipples + where they should be measured]

 

Step 4. Measure your nipple

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

Using a 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), and the big lines show every 10mm, which is 1 centimetre (cm). When you’re measuring, you just need to count every little line (the millimetres) from one side of the nipple to the other to figure out your nipple “size” or diameter.

[image of ruler]

[image of ruler along a nipple]

 

How and where to choose a flange

Now you have your diameter, add 2-4mm and choose the closest flange size available from your pump brand.

Here’s a table of pump brands and flange sizes available.

For example, if you think you need an 18mm or 19mm flange, but the smallest flange your pump comes with is a 21mm.

Each pump brand will have different instructions, so follow their advice on sizing, rather than just getting the standard size. You can see from the table above that the standard flange size that comes with most pumps is about 24mm. Some pumps send out two sizes with their pumps, and the second size is usually 28mm. 

Common flange questions

What’s a ‘normal’ nipple size – am I doing this right?

Women’s bodies are beautifully diverse. To give you an idea, nipple sizes might range from 5mm to 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 women 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.

Here’s a table of flange inserts and the sizes that they cover.

  • 18mm breast pump flange
  • 19mm breast pump flange
  • 20 mm breast pump flange
  • 20mm nipple what size flange
  • 22mm nipple shield
  • 24mm nipple shield
  • 24mm nipple size
  • 28mm nipple shield

Remember that your nipple size changes over time. Milkdrop can help here, because it’s so soft, it stretches to your shape, so you don’t have to keep buying different sizes as you move through your feeding and pumping journey. 

Measuring is confusing me. Is there another way?

You don’t have to tell us that measuring your nipple is a bit absurd!

On top of that, 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.

 

Some women find that Milkdrop cushions can help here. Because the silicone is so soft, it moulds to your nipple and areola. It will stretch if you have a larger nipple and compress around you if you have a smaller one. If you’re between sizes, unsure about sizing, or don’t want to buy different flange sizes as your nipple changes over time, it could be a good option. You can order whichever flange size your pump normally comes in, and then add a Milkdrop over the top, so you don’t need to size your nipple at all!

 

 

Pump sizing

  • how to pump – sizing
  • how to pump - flange sizing
  • Can breast pump flanges be too big
  • how to know if pump flange fits – “Pumps come with a variety of sized flanges, make sure you have the right size for your nipples, otherwise this can cause nipple damage and pain. You should aim to ensure that your nipples can move freely within the flange without rubbing, but making sure that not too much areola is being drawn up into the flange.”