About Cup Size Equivalents
Why Do Cup Letters Differ Between Countries?
One of the most confusing aspects of bra sizing is that the same cup volume can have completely different letter names depending on the sizing system used. A US "DD" cup is the same volume as a UK "DD" cup, but the next size up is US "DDD/F" versus UK "E". This inconsistency leads to widespread confusion, especially for online shoppers buying international brands.
The Four Main Sizing Systems
US Sizing: Uses double letters after D (DD, DDD/F) before switching to single letters (G, H, I…). This is the most idiosyncratic system.
UK Sizing: Uses double letters at specific points (DD, E, F, FF, G, GG, H, HH…). The UK system is favored by many bra fitting experts because it provides the most gradual size progression.
EU Sizing: Uses sequential single letters (D, E, F, G, H…). This is the simplest and most logical system, with no double letters.
French Sizing: Follows the same cup letter convention as EU sizing. The difference is in the band number, which is typically 15 more than the EU band.
Understanding Cup Volume Index
The cup volume index (0–15) represents the relative size of the cup, independent of the band size or the letter naming system. Each increment represents approximately 1 inch (2.54 cm) of difference between the bust and underbust measurements. Index 0 (AA) is the smallest, and index 15 (O) is the largest in this table.
Why Do Cup Letters Differ Between Countries?
One of the most confusing aspects of bra sizing is that the same cup volume receives different letter names depending on which country's sizing system you're using. A DD cup in the US is an E cup in the EU. A DDD in the US is an F in the EU but an E in the UK. This confusion leads to millions of women buying the wrong size when shopping internationally online.
The root cause is historical: each country's lingerie industry developed its own naming convention independently. There was never an international agreement on cup letter standards. The closest thing to a standard is the European EN 13402, but even this is not universally adopted.
The US Cup Letter System
The American system uses a combination of single and double letters. After D, it continues with DD, DDD (sometimes called F), and then G, H, I, J, K. The use of DDD instead of a single letter creates confusion because three-letter cup names are unique to the US system. Some US brands use F instead of DDD, but this is inconsistent across manufacturers. The progression after D represents approximately one additional inch of bust-to-band difference per increment.
The UK Cup Letter System
The British system is considered the most granular for cup sizing above D. It uses an alternating pattern of single and double letters: D, DD, E, F, FF, G, GG, H, HH, J, JJ, K. This alternating pattern provides more size options in the larger cup range, which is why UK brands like Bravissimo and Panache are popular among women with larger cup sizes. The double-letter system (FF, GG, HH, JJ) represents half-sizes between the single letters, effectively creating 15+ distinct cup sizes from AA to K.
The EU and French Cup Letter System
The European system is the simplest: straight sequential letters from A to O with no double letters. After D comes E, then F, G, H, I, J, K, L, M, N, O. This straightforward progression makes it easier to understand but offers fewer intermediate sizes compared to the UK system. The French system uses the exact same cup letters as the EU system — the only difference between French and EU sizing is the band measurement (French = EU + 15).
Cross-Reference: The Master Equivalence Table
Understanding the equivalence between systems is crucial for international bra shopping. At the DD level (5-inch difference), the US and UK both use DD, while the EU and FR use E. At the DDD level (6-inch difference), the US uses DDD, the UK uses E, and the EU/FR use F. At the 7-inch difference, the US uses G (skipping F), while the UK uses F, and the EU uses G. Our calculator shows these equivalences visually so you can instantly find your equivalent cup size in any system.
Practical Implications for Online Shopping
When shopping from international retailers, always check which sizing system the brand uses. A US-based brand selling a "DD" cup and a European brand selling an "E" cup are offering the same volume. If you're a US 34DDD shopping from a UK retailer like Figleaves, you should search for 34E. If shopping from a European retailer, look for 75F. Our cup equivalent calculator handles all of these conversions instantly, showing you the correct letter in every system.