Comprehensive Calculator Guide
This calculator suggests the right breast pump flange size from your nipple diameter in millimetres. The rule lactation consultants commonly use is a flange 2–4 mm wider than the nipple, so a 20 mm nipple suits a 22–24 mm flange. The right fit makes pumping comfortable and removes more milk; the wrong one can cause pain and damage.
Measuring and checking the fit
Measure the nipple alone at its base, not the areola, before pumping, since it swells during a session. Sizes can differ between breasts and change in the early weeks.
Too small rubs and pinches; too large pulls in much of the areola and can reduce output. With a good fit the nipple moves freely in the tunnel and pumping is comfortable.
How to Use
- Measure your nipple diameter at the base in millimetres, before pumping.
- Enter it in the calculator.
- Press “Find my size” to see the suitable range and the nearest common size.
Formula Used
Flange size ≈ nipple diameter + 2–4 mm
Practical Examples
- Example 1
- 20 mm nipple: 22–24 mm, nearest common size 24 mm.
- Example 2
- 16 mm nipple: 18–20 mm, nearest common size 19 mm; an insert may help with a 24 mm-only pump.
Important Tips
- Ask about other sizes when buying a pump.
- Start on low suction and raise it to the highest comfortable level.
- See a lactation consultant if pain continues.
Common Mistakes to Avoid
- Measuring the areola with the nipple.
- Measuring after pumping.
- Putting up with pain as normal.
Frequently Asked Questions
- What size do most pumps come with?
- Usually 24 mm, sometimes with 21 or 27 mm, which doesn’t fit everyone.
- Can each side need a different size?
- Yes; measure each separately.
- What if pumping hurts?
- Check size and suction first; see a doctor or lactation consultant if pain, redness or heat continue.