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We're working on a comprehensive educational guide for the Bra Size International Converter. Check back soon for step-by-step explanations, formulas, real-world examples, and expert tips.
The Bra Size International Converter translates band and cup sizes across six major sizing systems: US (28-46 band, AA-J cup), UK (28-46 band, AA-H cup with FF/GG/HH double-letter scheme), EU (60-105 band, AA-K cup), French (75-120 band, similar cup to EU but band numbering offset), Australian (6-24 band, AA-K cup), and Japanese (60-105 band, similar to EU). Despite same letter-and-number format appearing in multiple systems, each measures and labels differently — a US 34B is NOT a UK 34B in actual fit, and EU bands don't even use the same base numbers (60 cm vs 28 inches). Bra sizing standards developed independently in different regions during the early 20th century. US sizing emerged from Maidenform and Warner's in the 1930s. UK developed its own cup naming convention preserving traditional letter sequence (DD, DDD then E, F). EU/French uses metric measurements directly (band in cm). Modern Australian uses small integers (6-24) to band sizes. The international bra industry's persistent inability to standardize globally is partly cultural and partly serves marketing — each region's labels become familiar to consumers and create perceived value through brand association. Finding the right size has practical importance because bras affect comfort, support, posture, and clothing fit dramatically. Wacoal and other fitting studies have found 70-80% of women wear the wrong bra size — typically too-large band and too-small cup. Common pattern: someone measuring as 32D actually wears 36B which fits poorly (band too loose so cup pulls upward). Professional fitting is the gold standard, but international shoppers need conversion knowledge for online purchases from UK retailers (Bravissimo, Curvy Kate), US retailers (Victoria's Secret, ThirdLove), French (Chantelle, Simone Pérèle), and others. This calculator helps you convert between major systems for accurate international bra shopping. Enter band size and select system. Enter cup letter and select cup system. Calculator outputs equivalent band+cup sizes across US, UK, EU, French, Australian, and Japanese systems. Key conversion: US uses DD, DDD, E sequence; UK uses DD, E, F, FF, G, GG sequence; EU/French/Japanese use simple A-K sequence without double letters. Knowing these alphabetical differences is critical for international shopping accuracy.
Band Size: numerical conversion via lookup table; Cup Size: alphabetical conversion accounting for system-specific letter sequences
- 1Step 1 — Enter Your Known Band Size: Enter the numerical part of your current bra size (28, 30, 32, 34, etc. for US/UK; 60, 65, 70, 75 for EU/JP; 6-24 for Australian). Select which system this is from.
- 2Step 2 — Enter Your Cup Letter: Enter cup letter from your known size. Note: how cup letters extend differs across systems. US D, DD, DDD, F, G... UK D, DD, E, F, FF... EU D, E, F, G... — significant differences after D cup.
- 3Step 3 — Calculator Finds Closest Band Match: Calculator uses standard reference tables to match your band number to international equivalents. Each band row contains US, UK, EU, French, Australian, Japanese numbers for same underbust measurement.
- 4Step 4 — Calculator Maps Cup Across Systems: Uses standardized cup letter mapping. Critical insight: US DD = UK DD = EU E. US DDD = UK E = EU F. The pattern becomes clear with reference table familiarity.
- 5Step 5 — Review Combined Band+Cup in All Systems: Output displays your size in all 6 major international systems (US, UK, EU, French, Australian, Japanese) combined band+cup format. Use whichever system matches retailer you're shopping.
- 6Step 6 — Apply Sister Size Knowledge for Better Fit: If converted size doesn't fit, try sister sizes — same cup volume at different band. Sister sizes: 34C = 32D = 36B. Going down a band and up a cup is the most common adjustment when band feels loose.
Standard small/medium bra size — bands and cups align across systems at this level
Below D cup, most systems align (US/UK letters identical, EU shares letter). The number conversions vary by region: US 34 inches band = EU 75 cm band = French 90 (French adds 15 to EU number) = AU 12 (different scale). For online shopping, this size is widely available across most major international retailers.
At DD+ cups, US/UK use DD while EU/French use single letter E
This is where cup conversion becomes critical. US DD = UK DD (same convention) but EU/French/Japanese use single letter E. If you wear US DD and shop EU retailer, look for E cup, not DD cup. Many shoppers buy wrong size online because they assume DD is universal — it's not.
Standard EU size converts cleanly to other systems
EU 75D fits a 75cm (~30 inch) underbust measurement. Equivalent to US 34 inches band. D cup is universal across systems below DD. French numbering adds 15 to EU (90 = 75 + 15) for historical reasons. Australian uses a separate small-integer scale. Japanese typically follows EU.
Online shopping from international lingerie brands (Bravissimo, Chantelle, Triumph, Wacoal)
Travel where you need replacement bras in local sizing — Asia and Europe particularly require conversion
Comparing UK retailers (Bravissimo, Curvy Kate, Panache) vs US (Victoria's Secret, Aerie) sizing
Maternity and postpartum sizing as breast size changes through pregnancy and nursing
Specialty fits — sports bras, mastectomy bras, post-surgical recovery garments often use international sizing
| US | UK | EU/French/Japan |
|---|---|---|
| AA | AA | AA |
| A | A | A |
| B | B | B |
| C | C | C |
| D | D | D |
| DD | DD | E |
| DDD / E | E | F |
| F / G | F | G |
| G / H | FF | H |
| H / I | G | I |
| I / J | GG | J |
How do I measure my bra size correctly?
Underbust (snug, exhaling, ribcage just below bust): measure in inches or cm. Round to nearest even number = band size in US (e.g., 33 inches → 34 band). Bust (loose, standing straight, fullest point): measure in same unit. Subtract underbust from bust = difference. Each 1 inch difference = 1 cup letter (1=A, 2=B, 3=C, 4=D, 5=DD, etc.). Example: 30 inch underbust, 35 inch bust = 32 band, 4-inch difference = D cup → 32D. Most professional fitters use this method with adjustment for breast shape.
Why is sizing inconsistent across brands?
No regulatory standard. Each brand sets internal sizing within general regional convention. UK brands (Bravissimo, Panache, Curvy Kate) tend to run true to UK standards and offer widest size ranges. US brands (Victoria's Secret, Aerie) often vanity-size (run small numbers larger — your 'true' 32D measures more like 30DD in these brands). EU brands follow strict EU/ISO standards. Always check brand-specific size charts before purchasing.
Should I go up or down a band size?
Most fit advice: go down a band, up a cup. Modern professional fitting argues many women wear bands too loose. The band provides 80% of support — too loose means the bra rides up. Going from 36B to 34C (sister size) maintains cup volume with tighter, more supportive band. Common adjustment: if your band rides up or shoulder straps dig in, try smaller band number with larger cup letter (sister size up).
What is a sister size?
Sister sizes contain equal cup volumes at different band sizes. Going down a band, up a cup gives same cup volume with tighter band. Going up a band, down a cup gives same cup volume with looser band. Examples: 34B = 32C = 36A. 36DD = 34DDD = 38D. Useful when your size is unavailable — sister size up/down often fits when exact size missing.
Why do US brands use vanity sizing?
US bra brands historically realized customers psychologically prefer 'smaller band numbers' and 'larger cup letters' (32DD perceived more flattering than 36D). Brands adjusted internal sizing so customers measured 36D actually wear 32DD in their product. This creates inconsistency between brands and difficulty translating sizing. UK and EU brands have less vanity sizing pressure and tend to fit closer to professional fitting measurements. For accurate sizing, prefer UK/EU brands or professional fittings rather than self-sizing in US fast-fashion lingerie.
Pro Tip
Sister sizes contain equal cup volumes at different bands: 34C = 32D = 36B. If you know your size doesn't fit, sister-size up or down. UK retailers (Bravissimo specifically) carry the widest band/cup ranges if US options are limited at your size. Professional fittings (free at department stores like Nordstrom) provide the most accurate baseline size before shopping online.
Did you know?
The first modern bra was patented in 1914 by Caresse Crosby (born Mary Phelps Jacob), a New York socialite who created it from two silk handkerchiefs and ribbon for an evening dress. She sold the patent to Warner's for $1,500 (worth ~$45,000 today) — likely the worst patent sale in fashion history, as Warner's earned $15 million from it over the next 30 years. The cup-size letter system was introduced by Maidenform in the 1930s using A, B, C, D letters that have persisted globally for nearly a century despite multiple attempted standardizations. The system's longevity is largely cultural inertia — consumers know it intuitively and brands resist disruption.