EN

Bra size calculator – measure underbust and bust

Use this bra size calculator to find your size: measure around your ribcage directly under the bust and around the fullest part of the bust, enter both numbers and you instantly see band and cup – for example 34C – with conversions to other sizing systems.

Example: Unit: inches (in) · Underbust 29 in · Bust 35 in → Your bra size: 34B. Source: EN 13402-3, EN 13402 (CEN): Size designation of clothes – Teil 3: Maße und Intervalle; Übersicht mit BH-Band- und Cup-Stufen. Updated: .

in
Directly under the bust, tape level and snug, after breathing out
in
Around the fullest part of the bust, tape level and not pressing
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Result

Your bra size
34B
In other sizing systems
EU: 75B · UK: 34B · FR/ES/BE: 90B · AU/NZ: 12B · JP: C75
Sister sizes
If the band is too loose: 70C in EU sizing (one band smaller, one cup bigger). If the band is too tight: 80A in EU sizing (one band bigger, one cup smaller).
Working
Underbust 29 in → EU band 75 (5 cm steps, converted to US/UK). Bust 35 in − underbust 29 in = 6 in difference → EU cup B (2 cm per cup, from 10 cm = AA).
Sizes vary by brand and cut; use the result as a starting point and try bras on.

How it is calculated

How the bra size is calculated

A bra size has two parts: the band (number) and the cup (letter). The calculation follows the European clothing standard EN 13402:

Example: underbust 74 cm (29 in), bust 90 cm (35.4 in). The band rounds to EU 75, which is US/UK 34; the difference is 16 cm, which gives cup C – so 34C (EU 75C). As the standard describes it, size 70B fits an underbust of 68–72 cm and a bust of 84–86 cm.

How to measure

  1. Hold the tape level directly under the bust, snug but not cutting in, and read it after breathing out.
  2. For the bust, take the tape around the fullest part, also level and without pressing. Stand upright, without a padded bra.
  3. Enter both numbers in centimeters or inches. Half units are fine.

Sizing systems compared

EUUK/USFR/ESAU
70328510
75349012
80369514
853810016

Cups match up to D; after that the systems diverge: EU E equals UK DD, EU F equals UK E, and the US counts DD, DDD, then G. Japan steps cups in 2.5 cm and writes the letter before the number (C75).

Sister sizes

If the band is too loose, a smaller band with a bigger cup often helps (34B → 32C) because the cup volume stays the same. The other way round: a bigger band and a smaller cup (34B → 36A).

Limits

The calculator gives a starting point. Cut, fabric and brand change the fit, and breasts differ in shape and fullness. To convert measurements use the inches to cm converter; more calculators based on body measurements are the body fat calculator and the BMI calculator.

Frequently asked questions

How do I calculate my bra size?

Measure and enter your underbust and bust. The band comes from the underbust rounded to 5 cm, the cup from the difference between both measurements (2 cm per cup).

How do I measure underbust and bust correctly?

Keep the tape level: for the underbust directly under the bust, for the bust around the fullest part. It should be snug without cutting in.

What does 34B mean?

34 is the band (underbust of about 73–77 cm / 29–30 in), B the cup (a difference between bust and underbust of 14 to 16 cm).

How do I convert EU bra sizes to US or UK?

For the band, EU 70 is a 32, EU 75 a 34 and EU 80 a 36. Cups match up to D; EU E equals UK DD, EU F equals UK E.

What are sister sizes?

Sizes with the same cup volume but a different band: 34B, 32C and 36A suit the same breast volume. Useful if the band or cup does not quite fit.

Will the calculated size fit every brand?

Not always. Cut and fabric change the fit, so treat the result as a starting point for trying on.

Sources and legal basis

As of:

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