How do I measure my bra size?

Two measurements: (1) Band size: measure around your ribcage directly under your bust. Round to the nearest even number (add 1 inch if it's an odd number). This is your band size (32, 34, 36, etc.). (2) Cup size: measure around the fullest part of your bust. Subtract band size from bust measurement. Difference 1 inch = A cup; 2 inches = B; 3 inches = C; 4 inches = D; 5 inches = DD/E. Repeat measurements while wearing a non-padded bra.

What does it mean if a bra fits wrong?

Signs of incorrect bra size: straps digging in (band too big, straps overcompensating); band riding up (band too big); spillage over the top of cups (cup too small); gaping cups (cup too large); center gore not lying flat against the sternum (cup too small). Studies suggest 70–85% of women wear the wrong bra size. The most common error is too large a band and too small a cup — try sister sizes (e.g., go from 36C to 34D: same cup volume, different band).

What are sister sizes in bra sizing?

Sister sizes share the same cup volume with adjacent band sizes. Going up one band size = go down one cup letter. Going down one band size = go up one cup letter. Examples: 34D ↔ 36C ↔ 38B (same cup volume). 36DD ↔ 34E ↔ 38D. Sister sizes are useful when your measured size isn't available, or when a different band-to-cup balance is more comfortable.

Your Bra Size: 30DDD (US)

Your Bra Size

US Size

30DDD

United States

UK Size

30DDD

United Kingdom

EU Size

90F

European

FR/BE Size

105F

France / Belgium

Underbust (band)	75 cm
Bust (fullest)	90 cm
Difference	5.4 inches
US / UK Band Size	30
Cup (US/UK)	DDD
Full size US	30DDD
Full size EU	90F
Full size FR/BE	105F

Fit tips

The band should feel snug but not restrict breathing
If the band rides up in the back, try going down a band size and up a cup size (sister size)
If cups overflow or gape, adjust the cup size accordingly
Bra sizes can vary by brand — always try before buying

How Bra Sizing Systems Differ

Bra sizing is inconsistent across countries and brands. The US and UK use inch-based band sizes (32, 34, 36…) but different cup scales. Europe uses centimetre-based bands (70, 75, 80…). France and Spain use a different centimetre scale starting 15 units higher. A US 34C, UK 34C, EU 75C, and FR 90C all refer to very similar (but not identical) fits. Always measure yourself freshly before buying online and consult the brand's specific size chart.

International Bra Size Conversion

US	UK	EU	FR	AU
32	32	70	85	10
34	34	75	90	12
36	36	80	95	14

How Bra Sizing Works

Bra sizing combines two measurements: band size (the circumference of the ribcage just below the bust) and cup size (the difference between the bust circumference at its fullest point and the band size). In the US system, each inch of difference between bust and band corresponds to one cup letter: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, and so on. Band sizes are even numbers (32, 34, 36, 38, 40) and are derived by measuring in inches and rounding to the nearest even number.

Sister sizing is the concept that adjacent band sizes with the same cup volume exist. A 34C has the same cup volume as a 32D (one band size smaller, one cup larger) and a 36B (one band larger, one cup smaller). This matters when a preferred band size is unavailable — the cup volume remains equal.