US, UK, EU & International Sizing
Last reviewed: January 2026
Find your bra size from measurements and convert between US, UK, EU, French, and Italian sizing systems. This calculator runs entirely in your browser — your data stays private, and no account is required.
Bra sizing combines two measurements: the band size (ribcage circumference) and the cup size (the difference between bust and band measurements). Each inch of difference corresponds to one cup size — 1 inch = A, 2 inches = B, 3 inches = C, and so on.[1] Studies suggest that up to 80% of women wear the wrong bra size, most commonly with a band too large and a cup too small, because they rely on guesswork rather than measurement.[2] Sizing is not standardized across brands or countries — a 34D from one manufacturer may fit differently from another, and EU, UK, and US cup naming diverges significantly above a D cup.[3] Use the Body Weight Converter for related measurement conversions.
| US Size | UK Size | EU Size | Band (inches) | Bust (inches) |
|---|---|---|---|---|
| 32B | 32B | 70B | 32 | 34 |
| 34C | 34C | 75C | 34 | 37 |
| 36D | 36D | 80D | 36 | 40 |
| 38DD | 38DD | 85E | 38 | 43 |
| 40DDD | 40E | 90F | 40 | 46 |
Bra sizing combines two measurements — band size (the circumference around the ribcage directly below the breasts) and cup size (the difference between the bust measurement at its fullest point and the band measurement). Despite this seemingly simple system, an estimated 70–80% of women wear the wrong bra size, according to multiple fitting studies. The problem stems from inconsistent sizing standards across brands, reliance on outdated measuring methods, and the counterintuitive relationship between band and cup sizes.
Band measurement: Wrap a measuring tape snugly around your ribcage directly beneath your breasts, keeping the tape level and parallel to the floor. The tape should be firm against the skin without compressing. Round to the nearest even number — this is your band size in US sizing. If the measurement is odd, round up for comfort preference or down for support preference. Bust measurement: Measure around the fullest part of the bust with the tape resting gently without compressing breast tissue. Lean forward slightly to let gravity position the tissue naturally, which captures the fullest measurement. Cup size: Subtract the band measurement from the bust measurement. Each inch of difference corresponds to one cup size: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, 5 inches = DD/E, 6 inches = DDD/F, and so on.
One of the most misunderstood concepts in bra fitting is sister sizing — the fact that cup volume is not absolute but relative to band size. A 34C, 36B, and 32D all have the same cup volume despite different letter designations. Going up one band size and down one cup size (or vice versa) maintains approximately the same cup volume while changing the fit around the torso. This means a woman who measures as 34C but finds that band too tight might try 36B for a more comfortable fit while maintaining similar breast coverage. Understanding sister sizes dramatically expands your fitting options, especially when a brand runs small or large in particular sizes.
Bra sizing varies significantly across regions, causing confusion when shopping internationally or online. US/UK sizes use similar band numbering but diverge at larger cup sizes — US uses DD, DDD, DDDD (or G), while UK uses DD, E, F, FF, G, GG. European/Continental sizes (France, Spain, Belgium) add 15 to the US band number (so US 34 = EU 75) and use sequential lettering without double letters. Japanese sizes use a letter-number format (e.g., C75) where the cup letter comes first and the number is the European band equivalent. Australian sizes subtract 14 from the US band number (US 34 = AU 12). Always check the brand's specific size chart rather than relying on conversion tables, as even within the same sizing system, brands vary by 1–2 sizes.
Band riding up in back: The band is too large — try a smaller band (and up one cup letter to maintain volume). The band should sit level around the body on the loosest hook, allowing room to tighten as the elastic stretches over time. Underwire sitting on breast tissue: The cup is too small. The underwire should encircle the entire breast, resting flat against the ribcage at the sides and center. Gapping at the top of cups: Could indicate cup too large, wrong shape for your breast type, or bra designed for fuller-on-top projection. Spillage over the top or sides: Cup too small or style not designed for your breast shape. Center gore not tacking: The center piece between the cups should rest flat against your sternum — if it floats, the cups are likely too small.
Two women with identical measurements can need completely different bra styles because breast shape varies independently of size. Key shape factors include projection (how far breasts extend from the chest wall — shallow versus projected), fullness distribution (full on top versus full on bottom), root width (narrow versus wide base where breast meets chest wall), and set (close-set versus wide-set). Manufacturers design each bra style for a particular shape archetype. Finding brands and styles that match your shape is as important as getting the right size number.
Professional fittings at specialty lingerie stores remain the most reliable way to determine your optimal size and shape match — most offer complimentary fittings and can guide you toward styles engineered for your specific anatomy rather than relying on generalized size charts alone.
Bra sizing systems vary significantly across countries, which makes international shopping confusing. A US 34D is equivalent to a UK 34D but a European 75D and a Japanese E75. Cup progression also differs — US and UK systems both use letter increments, but diverge after D (US goes to DD/DDD, UK goes to DD/E/F). French and European sizing uses centimeters for band measurement and skips certain cup letters. If shopping from international brands, always consult the specific brand's size chart rather than relying on generic conversion tables. Our Clothing Size Converter handles the most common international size conversions.
See also: Clothing Size Converter · Shoe Size Converter · Ring Size Calculator
→ Cup size is relative to band size. A 32D and a 36D do not have the same cup volume. The 36D has a larger cup. "Sister sizes" — 32D, 34C, 36B — share similar cup volume on different band sizes. If your band is too tight, try a sister size up rather than just increasing the band.
→ 80% of women wear the wrong bra size. The most common error is a band too large and cups too small. Signs of poor fit: band rides up in back, straps dig in or fall off, cups wrinkle (too big) or overflow (too small), center gore doesn't lay flat.
→ Sizing varies significantly between brands. Use this calculator as a starting point, then try on. Different brands, styles, and even colors of the same bra can fit differently. Always try before buying, especially when switching brands.
→ Remeasure periodically. Bra size changes with weight fluctuation, hormonal changes, pregnancy, nursing, and aging. Remeasure every 6–12 months or whenever bras start fitting differently. See our Weight Converter for tracking changes.
See also: Clothing Size Converter · Shoe Size Converter · Ring Size Calculator · Unit Converter