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Flange Size Calculator

Health

Estimate the recommended breast pump flange size range from your nipple diameter measurement. A quick reference, not a lactation consultant fitting.

Reviewed by the thecalcu.com team · Last updated July 26, 2026

830

Recommended Flange Size

19
Typical Range (Low)
18
Typical Range (High)
20

This calculator computes your Recommended Flange Size, Typical Range (Low), Typical Range (High) from the values you enter.

Inputs
Nipple Diameter
Outputs
Recommended Flange SizeTypical Range (Low)Typical Range (High)

What is a Breast Pump Flange Size?

The Flange Size Calculator estimates a recommended breast pump flange size range from your measured nipple diameter, using common manufacturer guidance of adding roughly 2-4 mm for comfortable fit.

For related feeding tools, see the Baby's Milk Intake Calculator and Exclusive Pumping Calculator.

Why Use a Flange Size Calculator?

An ill-fitting flange is one of the most common causes of pumping discomfort and reduced output, and this calculator gives a quick starting reference from a simple nipple measurement to help narrow down the right size to try.

Who Should Use This Calculator?

  • New pumping parents looking for a starting reference flange size.
  • Anyone experiencing pumping discomfort who wants to check if their current flange size seems appropriate.
  • Parents shopping for pump flanges and unsure what size to order.
  • Lactation educators demonstrating basic flange fitting guidance.

What Insights Does the Flange Size Calculator Give You?

The Recommended Flange Size is the headline suggestion based on your nipple measurement. The Typical Range (Low) and Typical Range (High) figures show the broader range worth trying, since fit can vary by individual comfort and pump brand.

How to use this Breast Pump Flange Size calculator

  1. Measure your nipple diameter in millimetres, ideally right before a pumping session.
  2. Read the Recommended Flange Size and Typical Range instantly.
  3. Compare the result against your specific pump brand's available sizes.
  4. Consult a lactation consultant if you experience pain or reduced output, since individual fit can vary beyond this general estimate.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Recommended Flange Size = Nipple Diameter + 3 mm

Typical Range = Nipple Diameter + 2 mm to Nipple Diameter + 4 mm

Worked example, a nipple diameter of 16 mm:

Recommended Flange Size = 16 + 3 = 19 mm (range 18-20 mm)

Frequently Asked Questions

What is a breast pump flange?
A flange (or breast shield) is the funnel-shaped part of a breast pump that fits over the nipple and areola during pumping, getting the size right is important for comfort and effective milk expression.
How is recommended flange size calculated?
This calculator adds approximately 3 mm to your measured nipple diameter, reflecting common breast pump manufacturer guidance that flange size should be slightly larger than the nipple to allow comfortable movement during pumping.
How do I measure my nipple diameter?
Nipple diameter is typically measured across the base of the nipple (not including the areola) using a ruler or a printed nipple ruler tool, ideally right before a pumping session when the nipple isn't already stimulated.
Why is flange size larger than nipple diameter, not equal to it?
A flange that's too tight can cause pain, restricted milk flow, and nipple damage from friction, so common guidance recommends a small amount of extra room (about 2-4 mm) for comfortable movement during the pumping cycle.
What if my flange size seems too big or too small?
Signs a flange doesn't fit well include pain, reduced output, or nipple rubbing against the flange tunnel walls, if you experience these, trying a size within the suggested range, or consulting a lactation consultant, can help identify a better fit.
Is this calculator a substitute for a lactation consultant fitting?
This calculator gives a general starting reference based on a simple measurement. A lactation consultant can provide a hands-on assessment considering nipple elasticity, breast tissue, and pumping response, which this calculator can't capture.
Do flange sizes vary between pump brands?
Yes, different breast pump manufacturers may size their flanges slightly differently, so use this calculator's result as a general size target and check against your specific pump brand's sizing chart.
Can flange size need change over time?
Yes, nipple size can change during the breastfeeding or pumping journey due to factors like engorgement, weight changes, or simply adjusting over time, so it's worth re-measuring periodically if you notice changes in comfort or output.
How does this relate to the Baby's Milk Intake Calculator?
The [Baby's Milk Intake Calculator](/babys-milk-intake-calculator/) estimates how much milk a baby needs, while this calculator focuses on pump equipment fit, both are practical tools for parents navigating breastfeeding or pumping.
What units does this calculator use?
This calculator uses millimetres (mm) for both nipple diameter and flange size, matching how most breast pump manufacturers label their flange sizes.
Also known as
breast pump flange size calculatorflange fit calculatornipple size to flange sizepump flange sizing chart