Tools
Practical helpers you can use right here. Everything runs entirely on your own device — nothing you do on this page is recorded, saved, or sent anywhere.
Hold a standard card (credit, debit, ID) flat against your skin right beside your nipple, so both sit at the same distance from the lens. Get them both in frame, tap Freeze frame, then line up the card and drag the sizing circle — no fiddly sliders.
This is a live view only — nothing is ever captured, saved, or sent anywhere. The camera turns off the moment you leave this tool or switch modes.
Step 1 — Calibrate with a card
Grab any standard card (debit, credit, ID, gift card — they’re all the same size). Hold it flat against your screen next to the box below, and drag the slider until the box matches the card’s width exactly.
Step 2 — Read your size
Gently press against the screen near these circles — each one is sized to true scale now. Find the closest match, then confirm it below.
Dr. Lizzy’s take
Flange fit is the single most common thing people get wrong at the start, and it’s the easiest to fix. A size that’s off by a few millimetres turns a comfortable session into a painful one — it’s worth the two minutes to check.
Got your size?
Next step is picking a pump that actually fits your routine — and your budget.
Compare pumps