Bra Size Calculator
Enter your underbust and bust measurements to instantly get your cup size and convert between US, UK, EU/FR (France), IT (Italy), and AU (Australia) sizing systems. Free, no sign-up.
How to use
- 1Choose your measurement unit: Centimeters (cm) or Inches (in)
- 2Enter your underbust measurement — measured snugly around your ribcage just below your breasts
- 3Enter your bust measurement — measured around the fullest part of your chest
- 4Results auto-calculate: Cup size, Band size, and conversions for US, UK, EU, IT, AU systems
- 5View the full size chart and measuring guide
Frequently Asked Questions — Bra Size Calculator
What is the difference between US and EU bra sizes?+
Band sizes differ: US/UK use inches (32, 34, 36...), EU uses centimeters. The EU band size roughly equals the underbust in cm (e.g., 70cm underbust → EU 70). French (FR) sizing adds 15 to the US band. Example: US 34B = UK 34B = EU 75B = FR 90B = IT 3B.
How are cup sizes A, B, C, D calculated?+
Cup size = the difference between bust and underbust measurements. In US/UK: 1 inch difference = A, 2 = B, 3 = C, 4 = D, 5 = DD/E, 6 = DDD/F, and so on. Cup size is NOT an absolute measurement — a 34D is smaller than a 38D because the band is smaller.
What is a "sister size"?+
Sister sizes have the same cup volume but different band sizes. For example, 34C, 36B, and 32D are sister sizes — they all have the same cup volume. If the band is too tight, go up 1 band and down 1 cup (34C → 36B). If the band is too loose, go down 1 band and up 1 cup (34C → 32D).
Why does the same size fit differently across brands?+
Each brand cuts slightly differently, fabrics have different stretch, and cup shapes (full cup, plunge, demi) affect fit. Your calculated size is a starting point — try different brands and styles for the best fit.
How do I measure correctly?+
Underbust: exhale fully, measure snugly directly below your breasts. Round odd numbers up to the nearest even number. Bust: stand straight, measure around the fullest part, keeping the tape horizontal and not too tight. Wear a non-padded bra or none at all for accuracy.