Bra Size Calculator

How to Measure Band and Bust

Accurate measurements are the starting point. Two values are needed: your band measurement and your bust measurement.

Band measurement: Measure snugly around your ribcage just under the bust. The tape should be firm against the skin but not compressed. Exhale normally and record the reading in inches or centimetres.
Bust measurement: Measure around the fullest point of the chest, keeping the tape horizontal. The tape should not pull tight — it should sit against the skin without pressing in.

Keep the measuring tape level and parallel to the ground for both measurements. Small differences in tape position can affect the result.

How Bra Sizes Work

The band number (32, 34, 36…) is derived from the under-bust measurement, rounded to the nearest even number. The cup letter (A, B, C…) represents the difference between the bust and band measurements:

Difference (inches)	US / UK Cup Size
0	AA
1	A
2	B
3	C
4	D
5	DD
6	DDD / E

Sister Sizes

Sister sizes share the same cup volume with a different band size. If a 34C fits in the cup but the band feels too snug, a 36B uses the same cup volume with a larger band. The calculator shows both the smaller-band and larger-band sister sizes alongside your primary result.

When to Use This Calculator

Estimating size from measurements — convert two tape measurements into a standard size code
Checking size consistency — verify whether your current size matches your measurements
Converting between sizing systems — get the US, UK, and EU equivalents simultaneously
Quick reference before purchase — get an approximate size to use as a starting point when ordering

Important Note About Bra Sizing

Bra sizing can vary between brands, styles, and manufacturing standards. This calculator provides a standard size estimate based on the band-and-bust-difference method, which is the most widely used approach. Actual fit may differ depending on design, fabric, construction, and the specific brand's sizing conventions.

The result should be treated as a starting reference, not a guaranteed fit. Sizing marked identically across different products can feel noticeably different in practice.

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