Flange Size
Find your perfect breast pump flange size by nipple diameter. Free flange sizing tool with fit assessment for comfortable, efficient breast milk expression.
About This Calculator
The Breast Pump Flange Size Calculator helps breastfeeding mothers find the correct flange (breast shield) size for comfortable and efficient milk expression. Using the right flange size prevents nipple pain, abrasions, and clogged ducts while maximizing milk output.
This calculator uses the standard formula: recommended flange diameter = nipple diameter + 3 to 4 mm. The extra space allows your nipple to move freely inside the tunnel without friction while maintaining an effective vacuum seal.
How to measure your nipple size
- Use a ruler or measuring tape calibrated in millimeters.
- Measure the diameter of your nipple at its widest point (base), excluding the areola.
- Take the measurement before pumping when the nipple is not erect.
- Do not pull, stretch, or compress the nipple while measuring.
- Measure both nipples separately — it is common for sizes to differ.
Regional Notes
US: Flange sizes are typically available in 21, 24, 27, 30, 32, and 36 mm from brands like Medela, Spectra, and Lansinoh. Most insurance plans cover multiple flange sizes under the Affordable Care Act's breastfeeding support provisions.
UK: The NHS recommends proper flange fitting for all breastfeeding mothers using pumps. Flanges are available on prescription in some regions. Boots and John Lewis stock replacement flanges from major brands.
India: Breast pump flanges are available through online retailers like Amazon.in and FirstCry, with Medela and Spectra being the most widely available brands. Hospital lactation consultants can assist with sizing.
Frequently Asked Questions
What is a breast pump flange?
A breast pump flange, also called a breast shield, is the funnel-shaped plastic piece that sits over your nipple during pumping. It creates a vacuum seal that draws milk from your breast into the pump. Flanges come in different sizes, typically ranging from 21 mm to 40 mm in diameter.
How do I measure my nipple for flange size?
Use a ruler or measuring tape to measure the diameter of your nipple at its base, excluding the areola. Measure in millimeters. Do not pull or stretch your nipple. Take the measurement before pumping when the nipple is not erect. The average nipple diameter is around 17-23 mm, but sizes vary widely.
What size flange should I buy based on my nipple measurement?
Your flange should be 3-4 mm larger than your nipple diameter. For example, if your nipple measures 20 mm, look for flanges between 23-24 mm. Common flange sizes include 21 mm, 24 mm, 27 mm, 30 mm, and 36 mm. Choose the standard size closest to your recommended range.
What are the signs of a wrong flange size?
If the flange is too small: your nipple rubs against the tunnel walls, turns white or purple after pumping, feels compressed or painful, and you see reduced milk output. If the flange is too large: excess areola gets pulled into the tunnel, your nipple moves excessively, you experience discomfort, and milk may not be fully expressed. Either case can lead to clogged ducts or mastitis over time.
Can I use different flange sizes on each breast?
Yes, it is common for nipples to differ slightly in size between breasts. Many pumping mothers use different flange sizes on each side for optimal comfort and milk output. Measure each nipple separately and choose the corresponding flange size for each breast.
Is a 24 mm flange considered standard?
Yes, 24 mm is the most common flange size and comes standard with most breast pumps. However, studies show that up to 80% of women may need a different size. Do not assume the standard flange fits—measure your nipple diameter and use this calculator to find your ideal size.
Where can I buy breast pump flanges in different sizes?
Breast pump flanges in various sizes are available at major retailers like Amazon, Target, and Walmart in the US; Boots and John Lewis in the UK; and FirstCry and Amazon.in in India. Most pump manufacturers (Medela, Spectra, Philips Avent, Lansinoh) sell compatible flanges separately. Nipple sizing kits are also available to help you find the perfect fit.