Bra Size Calculator

Professional-style fitting: primary band and bust, optional triple underbust and triple bust averages, centimetres or inches, and US / UK / EU / AU labels. Results are educational — always try bras on; brands vary.

Measurement inputs

Multi-method averages match common pro fitting workflows.

Units

Primary method

Band size (underbust) (in)

Snug, horizontal tape under the bust.

Bust size (overbust) (in)

Fullest point, tape parallel to floor.

Breast shape (optional)

Please adjust

Enter a valid underbust / band measurement.
Enter a valid bust measurement.

Measurement guide (diagrams)

Vector-style steps show tape placement. Use the interactive diagram to reinforce where each reading comes from.

Underbust (band)

Wrap the tape around your ribcage directly under the bust. It should be horizontal and comfortably snug.

Bust (overbust)

Measure around the fullest part — usually across the nipple line — while standing straight.

Interactive guide — tap a zone

Dashed lines animate to show where the tape should sit.

Frequently asked questions

Why three bust measurements?: Standing, leaning, and lying capture how breast tissue redistributes. Averaging can stabilise cup estimates when fullness varies.
Are US and UK bra sizes the same?: Band numbers often match on dual-label bras. Cup letters can differ above a D depending on the brand and market — we show a typical UK mapping next to US.
How do EU sizes work?: EU bands are a different number scale (for example 75 instead of 34). Cup letters are often shown alongside the EU band on tags.
What is a sister size?: Going up one band size and down one cup letter (or the reverse) keeps roughly the same cup volume with a different band tightness.

Quick tips

Use a soft tape; keep it level all the way around.
Advanced fields are optional but improve confidence.
Try the calculated size and one sister size when shopping.

Sister sizes

If the band feels tight but the cup is right, try +2 band and one cup smaller (e.g. 34C → 36B).