Calculate an initial bra size estimate and use fit diagnostics to refine final size.
A bra size calculator estimates starting size from ribcage (underbust) and full bust measurements.
Sizing varies by brand and style, so fit checks remain essential even when measurements are accurate.
Tape level around ribcage directly under breast tissue.
Measure at fullest point with tape parallel to floor.
Round underbust using local sizing convention.
Compute bust minus band difference.
Convert difference to cup progression for region system.
Check band tension, strap support, gore tack, and cup overflow.
Cup Difference = Bust - Band; Cup Letter maps to difference increments
Bra sizing combines a numeric band measurement with a cup category derived from the bust-to-band difference.
Diff = 35 - 32 = 3 in
Approx size: 32C (brand-dependent)
Go down band, up cup letter
Try 32DD as sister size
Convert to regional chart and cup progression
Estimated regional size range shown by calculator