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Bra Size Converter

Converter
Sizing note
Bra sizing varies between brands. Use these conversions as a guide and consult the specific brand's size chart when purchasing.

Select your source system, band size, and cup size, then press Convert to see results in all systems.

About This Tool

Bra Size Converter – Convert Between US, UK, EU, FR, IT, AU and JP Sizing

Finding the right bra when shopping internationally or switching brands can be confusing because every country uses its own sizing standard. A 34C in the US is the same cup volume as a 75C in Europe, yet the numbers look completely different. This Bra Size Converter translates sizes across seven major international systems — US, UK, EU, French, Italian, Australian, and Japanese — so you can shop with confidence regardless of where the product is made.

Which Sizing Systems Are Supported?

The converter handles the following international bra sizing standards:

  • US – Uses inch-based band sizes (28–42) and cup letters with Anglo progression including DD, FF, GG, and HH.
  • UK – Identical band and cup progression to US sizing. The same number and letter in UK and US represent the same size.
  • EU – European standard with centimetre-based band sizes (60–95 in 5 cm steps) and a continuous A–M cup alphabet without double letters.
  • FR – French and Belgian sizing adds 15 to the EU band number. EU 75 equals FR 90. Cup letters follow the same continuous EU progression.
  • IT – Italian sizing adds 5 to the EU band number. EU 75 equals IT 80. Same continuous cup letter system as EU and FR.
  • AU – Australian sizing mirrors US and UK band and cup progressions exactly.
  • JP – Japanese sizing uses centimetre-based band numbers identical to EU, with a continuous cup alphabet matching the EU system.

How Band Sizes Are Converted

Band sizes represent the measurement around the ribcage just below the bust (the underbust). Each band tier corresponds to a centimetre range:

  • US/UK/AU 34 = EU/JP 75 = FR 90 = IT 80 — all indicate an underbust of approximately 73–77 cm.
  • US/UK/AU 36 = EU/JP 80 = FR 95 = IT 85 — underbust of approximately 78–82 cm.

The converter normalises your band size to an underbust centimetre value and maps it to the equivalent band number in the target system.

How Cup Sizes Are Converted

Cup letters represent the difference between the overbust (fullest part of the bust) and the underbust. Each cup step is approximately 2.5 cm of difference. The US and UK systems use double letters at certain points (DD, FF, GG) while EU, FR, IT, and JP use a continuous single-letter progression (E, F, G). A US/UK DD equals EU E, a US/UK FF equals EU G, and so on. The converter maps cup letters by volume index so the conversion is accurate across both progressions.

Sister Sizes: Alternatives When Your Size Is Out of Stock

Sister sizes are bra sizes that share the same cup volume but use a different band size. Going down one band size and up one cup letter — or up one band and down one cup — preserves the cup volume. For example:

  • 32D → 34C → 36B — all three have the same cup volume.
  • A tighter sister size (smaller band, larger cup letter) gives more lift.
  • A looser sister size (larger band, smaller cup letter) gives a softer feel.

The Sister Sizes panel shows the two adjacent sister sizes in your source system whenever you perform a conversion.

Finding Your Size from Measurements

If you do not know your size in any system, use the From Measurements tab. Enter your underbust and overbust measurements in centimetres or inches. The tool calculates the cup difference and recommends your size in all seven systems simultaneously. For accurate measurements:

  • Measure your underbust by wrapping the tape firmly around your ribcage directly beneath your bust. Keep the tape parallel to the floor and breathe normally.
  • Measure your overbust around the fullest part of your bust, keeping the tape horizontal. Do not pull too tight.
  • Wear a non-padded bra or measure over light underwear for the most representative result.

Why Bra Sizing Differs Between Countries

Bra sizing systems developed independently in different countries without an international standard. The UK and US systems both trace their origins to inch-based measurement traditions and share the same numeric and letter scale. The continental European system was designed around metric measurements, assigning the underbust centimetre measurement directly as the band number. France added an offset to create its own scale, and Italy did the same. Japan adopted a system based on European metric sizing. Because these systems developed separately, there is no single arithmetic formula that converts all of them — the converter uses lookup tables aligned to the same underbust cm reference, which is the most reliable approach for consistent results.

Tips for Accurate International Bra Shopping

A size conversion gives a strong starting point but fit also depends on bra style, fabric, cut, and brand. Keep these points in mind:

  • Check the specific brand's size chart if one is available, since premium and designer brands often use their own measurements.
  • Underwired styles typically run truer to the conversion result than wireless or stretch bras, which have more tolerance.
  • If you are between band sizes, try both and choose the band that feels snug without digging in — a properly fitting band provides most of the support.
  • Cup volume changes with band size even when the cup letter stays the same, so always re-verify when switching between band sizes.

Frequently Asked Questions

Is the Bra Size Converter free?

Yes, Bra Size Converter is totally free :)

Can I use the Bra Size Converter offline?

Yes, you can install the webapp as PWA.

Is it safe to use Bra Size Converter?

Yes, any data related to Bra Size Converter only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

How does this bra size converter work?

The converter normalises your band size to an underbust measurement in centimetres and maps your cup letter to a cup-volume index. It then looks up the equivalent band number and cup letter in the target sizing system using standard international lookup tables. Both band and cup conversions are handled independently so the final result matches the correct size label in the chosen system.

Which sizing systems are supported?

The converter supports seven major international standards: US, UK, EU (European), FR (French/Belgian), IT (Italian), AU (Australian), and JP (Japanese). These cover the sizing systems used in the vast majority of international online shopping and retail stores.

What are sister sizes and when should I use them?

Sister sizes are bra sizes with the same cup volume but a different band size. For example, 34C, 32D, and 36B all have approximately the same cup volume. If your exact converted size is unavailable in a store, a sister size with a tighter or looser band will give a similar cup fit. Use the Sister Sizes panel to see the adjacent options above and below your size.

How accurate are the size conversions between systems?

The conversions follow widely accepted band-to-centimetre mappings and cup-letter progressions used by major manufacturers. Because bra sizing is not formally standardised across countries, minor differences exist between brands. Use these results as a reliable starting guide and consult the specific brand's size chart when available.

Can I enter my measurements to find my size?

Yes. Enter your underbust and overbust measurements in centimetres or inches using the Raw Measurements mode. The tool calculates the cup difference and recommends your size in all supported systems. For best results, take measurements over light-fitting underwear with a non-stretch tape measure.

Why does the same cup letter mean different things in different countries?

Cup letters represent a volume difference between the underbust and overbust measurements, but countries use different letter sequences. The US and UK share a similar progression (A, B, C, D, DD, E, F…) while EU, French, Italian, and Japanese systems use a continuous alphabet (A, B, C, D, E, F, G…). A US/UK DD equals an EU E. This converter handles those differences automatically.