The Ultimate Guide to International Bra Size Conversion
Did you know that over 80% of women wear the wrong bra size? The confusion is often compounded when shopping for international brands. A 34C in the US is not the same as a 34C in France or Australia. Our bra size converter eliminates the guesswork, instantly translating your measurements across US, UK, EU, French (FR), Italian (IT), Australian (AU), and Japanese (JP) sizing systems.
Why Standards Differ
The root of the confusion lies in how different regions calculate the Band Size.
- US & UK: Traditionally added +4 inches to the underbust measurement (e.g., 30" ribcage = 34 band). Modern fitting often ignores this, but labels remain.
- EU (Europe): Uses centimeters and subtracts ~5cm from the ribcage measurement (e.g., 75cm ribcage = 75 band), creating a built-in offset.
- France/Spain: Adds 15cm to the EU size (e.g., EU 75 = FR 90).
- Italy: Uses ordinal numbers (1, 2, 3...) instead of cm or inches.
The "Sister Size" Secret
If your calculated size doesn't feel right, you might need a Sister Size. Sister sizes are groups of bra sizes that share the same physical cup volume but have different band lengths.
How it works:
- If the band is too tight, go UP a band and DOWN a cup.
- If the band is too loose, go DOWN a band and UP a cup.
(All three have the same cup volume!)
How to Measure for the Perfect Fit
Step 1: Your Band Size (Underbust)
Stand straight without a bra or wearing a non-padded one. Wrap a measuring tape firmly around your ribcage, directly under your bust where the bra band would sit. Ensure the tape is level and parallel to the ground.
US/UK:If even, add 4 inches. If odd, add 5 inches. (e.g., 29" → 34 band).
Note: Many modern fitters skip the +4 rule. Our calculator supports both standard and modern logic.
Step 2: Your Cup Size (The Difference)
Measure loosely around the fullest part of your bust. Keep the tape straight across your back.
Calculation: Bust Measurement - Band Measurement = Cup Factor.
- 1" = A Cup
- 2" = B Cup
- 3" = C Cup
- 4" = D Cup
- 5" = DD/E Cup
- 6" = DDD/F Cup
Troubleshooting Common Fit Issues
🛑 Band Riding Up
The band is too loose. It should sit horizontally across your back. Try a smaller band size.
🛑 Cups Gaping
The cups are too big, or the style is wrong for your breast shape. Try a smaller cup or a demi-cup style.
🛑 Middle Gore Floats
The center piece should lie flat against your sternum. If it floats, the cups are likely too small.
Pro Tip: Brand Variations
Even with a perfect measurement, size varies by brand. Victoria's Secret tends to have stretchier bands (size down), while strictly European brands like Chantelle or Prima Donna may run firmer. Always check specific brand charts if available.