Choosing your Pump Size: 3 Easy Steps to the Getting Your Right Fit

Finding the right pump flange size is one of the most important steps to making pumping more comfortable and effective. But figuring out your “Goldilocks fit”—where your pump flange fit is just right—can feel overwhelming at first. In this blog, I’ll walk you through 3 simple steps to help you measure, experiment, and find the perfect fit for your body.

Step 1: Get the Right Ruler for Your Pump Flange Fit

To get a custom fit for your pump, you need to measure your nipple size accurately. The easiest way to do this is by using a nipple-sizing ruler, which you can print at home or purchase online. If you don’t have one yet, download my printable flange sizing guide here.

When printing a guide, make sure it’s to scale—use a ruler to confirm that the measurement box on the page matches its labeled dimensions. Even small inaccuracies in printing can lead to the wrong pump flange fit. Alternatively, you can purchase a metric circle ruler for under $10 or use digital calipers if you have them.

💡 Expert Tip: Your goal is to find the diameter of the widest part of your nipple (in millimeters). This nipple measurement will guide you toward your initial flange size and ensure pumping comfort.

Step 2: Measure Accurately for a Comfortable Pumping Experience

Once you have your ruler, it’s time to measure. Cut out the holes in the sizing guide and slide the ruler over your nipple to find the closest fit. Make sure it feels snug but not tight, and avoid including your areola in the measurement. The goal is to measure only the nipple itself, as this is the part that stretches during pumping.

If you’re using digital calipers, lightly rest the tool around your nipple without compressing it. Write down the nipple measurement you find—this is your starting size for a better flange fit.

💡 Expert Tip: Eyeballing your nipple size won’t give you an accurate result. If someone offers a flange size suggestion without actually measuring you, they’re guessing—and that could lead to discomfort or reduced milk removal.

Step 3: Find Your Custom Fit

Now that you know your nipple size, it’s time to experiment. Pump flange sizing isn’t one-size-fits-all—your body’s response to pumping can vary. For example, some people’s nipples swell during pumping and may need a larger size, while others may find a smaller size works better as their nipples stretch. Start with the flange size closest to your nipple measurement and adjust as needed.

The chart below is a good starting point for where to start with finding your best fit.

Think of it as your own science experiment! Try different sizes for a few sessions, noting how they feel and how much milk you produce. The right pump flange fit will maximize milk removal while staying comfortable and preventing damage.

💡 Expert Tip: If pumping feels uncomfortable or you notice swelling, bruising, or pain, stop and try a different size. Catching these issues early can prevent long-term damage.

Pro Tips for Better Pump Flange Sizing

Once you’ve measured and started experimenting with flange sizes, there are a few extra considerations to keep in mind:

Your Body Isn’t Symmetrical

It’s completely normal for your nipples to be different sizes or for one side to produce more milk than the other. You may need different flange sizes for each side to achieve the best results.

Postpartum Swelling Can Affect Your Pump Flange Fit

The size that works for you immediately after delivery may not be the size you’ll need long-term. Fluid retention from pregnancy or IV fluids during labor can temporarily change the size and elasticity of your breast tissue.

Seek Professional Support if You Need It

Measuring your nipple size can be tricky, especially if it’s hard to see or access the area. A lactation consultant can help ensure accurate measurements and troubleshoot any issues with pumping comfort or fit.

Final Thoughts

Pumping is a personal journey, and finding the right pump flange size takes time and patience. By taking the time to measure accurately, experiment thoughtfully, and adjust as needed, you’re setting yourself up for a more comfortable and successful pumping experience.

Every session is progress, and you’re doing amazing. Take it one step at a time—you’ve got this

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Have More Questions? Check Out These Related Resources:

• 5 Tips to Pump More Milk & Reduce Stress