Bra Size Converter
Convert bra sizes between US, UK, EU, FR/BE, and JP sizing systems.
About this tool
Bra sizing systems vary dramatically across the world, making it difficult to find the right fit when shopping internationally or buying from overseas retailers. This converter helps you navigate the differences between US, UK, EU, French/Belgian, and Japanese sizing standards, ensuring you can confidently purchase the correct size no matter which country's system you're using. Understanding your size in multiple formats is essential for anyone who shops across borders or travels frequently.
To use the converter, simply select your current size using the dropdown menus for band size and cup size, then choose which system you're converting from. The tool instantly displays the equivalent sizes in all other major sizing systems. Whether you're converting from your familiar US size to EU for a European boutique, or from UK to Japanese for online shopping, the conversion happens immediately without any manual calculations needed.
Frequently Asked Questions
Code Implementation
# Bra Size Converter: US/UK/EU/FR/AU/JP band and cup systems
# Band size conversion (US/UK inches β EU/FR cm-based number)
# US/UK band β EU/FR: multiply by 2.54, then round to nearest 5 (add ~1)
# EU band β US/UK: divide by 2.54 (round to nearest even)
EU_BAND_TABLE = {
28: 60, 30: 65, 32: 70, 34: 75, 36: 80, 38: 85,
40: 90, 42: 95, 44: 100, 46: 105, 48: 110,
} # US/UK β EU
# Cup conversion: US cup letters match UK, but EU/FR is one step up
# US/UK A β EU/FR B, US/UK B β EU/FR C, etc.
CUP_LETTERS = ['AA', 'A', 'B', 'C', 'D', 'DD', 'E', 'F', 'G', 'H']
def us_band_to_eu(us_band: int) -> int | None:
return EU_BAND_TABLE.get(us_band)
def eu_band_to_us(eu_band: int) -> int | None:
reverse = {v: k for k, v in EU_BAND_TABLE.items()}
return reverse.get(eu_band)
def us_cup_to_eu_cup(us_cup: str) -> str:
"""US/UK cup β EU cup (one letter up)."""
idx = CUP_LETTERS.index(us_cup.upper()) if us_cup.upper() in CUP_LETTERS else -1
if idx == -1:
return "?"
eu_idx = min(idx + 1, len(CUP_LETTERS) - 1)
return CUP_LETTERS[eu_idx]
def find_sister_sizes(band: int, cup: str, count: int = 3) -> list[str]:
"""Return sister sizes (same cup volume, different band/cup combos)."""
cup_idx = CUP_LETTERS.index(cup.upper()) if cup.upper() in CUP_LETTERS else -1
if cup_idx == -1:
return []
sizes = []
bands = list(EU_BAND_TABLE.keys()) # US band values: 28,30,...,48
for b in bands:
diff = (b - band) // 2 # band step of 2 inches
cup_i = cup_idx - diff
if 0 <= cup_i < len(CUP_LETTERS):
sizes.append(f"{b}{CUP_LETTERS[cup_i]}")
return sorted(sizes, key=lambda s: abs(int(s[:-1]) - band))[:count*2-1]
# Example
us_band, us_cup = 34, 'B'
eu_band = us_band_to_eu(us_band)
eu_cup = us_cup_to_eu_cup(us_cup)
print(f"US/UK: {us_band}{us_cup}")
print(f"EU/FR: {eu_band}{eu_cup}")
print(f"Sister sizes: {find_sister_sizes(us_band, us_cup)}")
# US/UK: 34B
# EU/FR: 75C
# Sister sizes: ['34B', '36A', '32C', '38AA', '30D']Comments & Feedback
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