Bra Size Converter
Convert bra sizes between US/UK, EU, FR/ES, AU/NZ, and JP sizing systems, or estimate your size from bust and underbust measurements. Supports UK double letters (DD, FF, GG) and single-letter cups, calculates sister sizes for alternate fits, and offers modern or traditional band rounding rules. All calculations happen in your browser for complete privacy.
How it works: Enter your current bra size to convert across regions, or provide your underbust and bust measurements to estimate a size. We align your measurements to standard band ladders (US/UK in inches, EU/JP in 5cm steps) and map cup sizes from the bust-underbust difference. Sister sizes show alternate band-cup combinations with the same volume. All calculations run locally in your browser.
What Is a Bra Size Converter?
A bra size converter translates bra sizing between the different systems used in the US, UK, Europe, France, Australia, and Japan. Each region uses a different formula for band size (the number) and sometimes different cup letter progressions, making international shopping confusing. A US 34C is not the same fit as what a European shopper might call a 75C without understanding the conversion.
This converter also helps with measuring and calculating your size from underbust and bust measurements — particularly useful since most women wear an incorrect bra size due to outdated fitting methods or inconsistencies between brands.
How to Use This Bra Size Converter
- Select your known size system (US, UK, EU, FR, AU) and enter your current size.
- The converter shows your equivalent size in all other regional systems.
- To measure from scratch: measure your underbust (band size) and your fullest bust measurement in inches.
- Calculate cup size: bust − underbust. Each inch = one cup size (1″ = A, 2″ = B, 3″ = C, etc.).
- Check sister sizes if your calculated size is unavailable — go up one band and down one cup, or vice versa, for the same cup volume.
Worked Example: US 34C in All Systems
Starting size: US 34C
US: 34C
UK: 34C (same as US)
EU: 75C (band = underbust in cm, rounded to nearest 5)
FR/ES: 90C (band = EU + 15)
AU: 14C (AU band = US band ÷ 2 − 4, approximately)
JP: B75 (cup letter first, then EU band)
Sister sizes with same cup volume: 32D (smaller band) | 36B (larger band)
Band Size Conversion Table by Region
| US / UK Band | EU Band | FR / ES Band | AU Band | JP Band |
|---|---|---|---|---|
| 28 | 60 | 75 | 6 | 60 |
| 30 | 65 | 80 | 8 | 65 |
| 32 | 70 | 85 | 10 | 70 |
| 34 | 75 | 90 | 12 | 75 |
| 36 | 80 | 95 | 14 | 80 |
| 38 | 85 | 100 | 16 | 85 |
| 40 | 90 | 105 | 18 | 90 |
| 42 | 95 | 110 | 20 | 95 |
Cup letters (A, B, C, D, DD/E) are the same across US, UK, and AU systems. EU and FR use the same cup letters. JP uses the same cups but lists the letter before the band number.
Key Concepts: Band Fit, Cup Volume, and Sister Sizes
The band provides 80% of support in a well-fitting bra. The band should feel snug enough that you can fit only two fingers underneath it, and should sit parallel to the ground around your ribcage. A too-loose band rides up the back; a too-tight band digs in and restricts breathing. Most bras are designed to be worn on the loosest hook when new, allowing tightening as the band stretches with wear.
Cup size is relative to band size, not absolute. A 32D cup is physically smaller than a 36D cup, even though both are labeled D. Cup size represents the difference between bust and band measurements. A 34C and a 36B contain the same cup volume — these are sister sizes. Understanding sister sizes is useful when a specific band/cup combination is out of stock.
UK and US bra sizes differ in cup labeling above D. In the US, the sequence goes: A, B, C, D, DD, DDD/E, DDDD/F. In the UK: A, B, C, D, DD, E, F, FF, G, GG, H. A US DD equals a UK DD/E; a US DDD/E equals a UK F. European (EU/FR) systems use a similar sequence to UK but with different notation for larger cups.
Tips for Finding the Right Bra Fit
Measure yourself every year. Weight fluctuations of as little as 5–10 lbs can change your bra size. Pregnancy, nursing, and hormonal changes also affect sizing. Many women continue wearing sizes from years past that no longer fit correctly. Professional bra fitting is available for free at most lingerie specialty stores.
Add-3 or add-4 methods are outdated. The traditional method of adding 4–5 inches to your underbust measurement for band size was developed for bras with less stretch. Modern bras use stretchier fabrics. Measure your underbust tightly; if it is even (e.g., 32″), that is your band size. If it is odd (e.g., 33″), round up (34). Do not add extra inches.
Different brands vary significantly. Bra sizing is not standardized across manufacturers. Always check brand-specific size charts and review fit guides. Consider that fit varies by style (push-up, sports bra, balconette, t-shirt bra) even within the same brand. Ordering multiple sizes for home try-on is the most reliable way to find the best fit.
Frequently Asked Questions
How do I convert US bra size to EU?
The EU band size equals your underbust measurement in centimeters, rounded to the nearest 5. US 32 band = 70 EU; US 34 = 75 EU; US 36 = 80 EU. The cup letters are the same (A, B, C, D, DD). So US 34C = EU 75C. French/Spanish sizing adds 15 to EU band: FR 90C = EU 75C = US 34C.
What are sister sizes?
Sister sizes have the same cup volume but different band sizes. Going up one band and down one cup — or down one band and up one cup — gives you the same volume in a different fit. Example: 34C, 32D, and 36B are sister sizes. Use a sister size when your ideal size is unavailable or when you want a tighter/looser band while maintaining the same cup volume.
How do I measure my bra size at home?
Use a soft measuring tape. Step 1: Measure your underbust (directly under your bust) snugly — this is your band size. Round to nearest even number. Step 2: Measure your fullest bust loosely. Step 3: Subtract underbust from bust. Every inch = one cup size: 1″=A, 2″=B, 3″=C, 4″=D, 5″=DD. Example: 32″ underbust + 35″ bust = 3″ difference = 32C.
Is UK 34C the same as US 34C?
For sizes up to D cup, US and UK sizes are identical. Above D, the labeling diverges. US DD = UK DD; US DDD/E = UK E/F; US DDDD/F = UK F/FF. So US 34DD = UK 34DD, but US 34DDD = UK 34E/F. When shopping from UK brands or US brands, check their specific size guide above DD.
Why do bra sizes differ between brands?
Bra sizing is not standardized. Different manufacturers use different patterns and materials, so a 34C from Brand A may fit very differently from Brand B's 34C. Additionally, some brands use vanity sizing (making sizes run larger to flatter customers). Always try on bras or check brand-specific fit guides and customer reviews for sizing notes.
What is the difference between cup sizes across countries?
US, UK, and Australian cup letters follow similar progressions (A, B, C, D, DD). EU/FR systems use the same letters but label beyond DD differently (E instead of DD, F instead of DDD). Japanese bras label cups before the band (e.g., B75 instead of 75B) and may use different letter progressions for larger sizes. Always check a specific conversion chart for sizes above DD.
How does bra sizing change during pregnancy?
During pregnancy, the band size typically increases 1–2 sizes due to rib cage expansion, and cup size increases 1–3 cups as breast tissue grows. Sizing often changes during each trimester. Maternity bras are designed with extra row of hooks and stretchy fabric to accommodate changes. Nursing bras add drop-down cups. It is recommended to get professionally fitted during the second trimester when initial growth stabilizes.
What does the +3 or +4 bra fitting method mean?
The add-3 or add-4 method (adding inches to underbust) was developed when bras were less stretchy. It results in too-loose bands for most modern bras. Contemporary fitting professionals recommend measuring underbust snugly and using that directly as your band size (rounding to nearest even number). The tight-band, larger-cup approach provides better support than loose-band, smaller-cup.