Fashion Sizing & Fit Science
Bra Size Calculator & Sister Chart
Measure underbust ribcage and fullest bust to determine exact band and cup size. Convert US, UK, and European sizes and calculate sister sizes for optimal comfort.
Interactive Sizing & Sister Size Engine
Calculate Band & Cup Size Instantly
Measure snug underbust for band size, then measure fullest bust circumference. The difference in inches defines your cup volume.
34"
28" (XS)34" (M)44" (Plus)
37"
Diff: +3"Volume: Cup C
Calculated Primary Bra Size
34C
🇺🇸 US/UK: 34C🇪🇺 EU: 75C🇫🇷 FR: 90C
🔄 Sister Sizes (Same Cup Volume, Different Band Tightness):Tight Band: 32D • Loose Band: 36B
Bust to Ribcage Difference Chart:
| Cup Size | Difference (Inches) | Difference (cm) | UK Equivalent | EU Equivalent |
|---|---|---|---|---|
| AA | 0.5" difference | ~1.5 cm | AA | AA |
| A | 1" difference | ~2.5 cm | A | A |
| B | 2" difference | ~5 cm | B | B |
| C | 3" difference | ~7.5 cm | C | C |
| D | 4" difference | ~10 cm | D | D |
| DD / E | 5" difference | ~12.5 cm | DD | E |
| DDD / F | 6" difference | ~15 cm | E | F |
| G | 7" difference | ~17.5 cm | F | G |
| H | 8" difference | ~20 cm | FF | H |