Bra Size Calculator vs Ring Size Converter

Measure your band by wrapping a tape measure snugly around your ribcage just under your bust. Measure your bust loosely around the fullest point. The difference in inches determines your cup size: 1 inch = A, 2 = B, 3 = C, etc.

Sister sizes have the same cup volume but different band sizes. If 34C is too tight in the band, try 36B (one band up, one cup down). If too loose, try 32D (one band down, one cup up).

Wrap a string or paper strip around the base of your finger, mark where it overlaps, then measure the length in millimeters. Divide by 3.14 to get the diameter. Alternatively, measure the inside diameter of a ring that fits well. For accuracy, measure at the end of the day when fingers are largest, and measure 3-4 times.

US and UK ring sizing systems use different scales. US sizes run from approximately 3 to 13, while UK sizes use letters (A to Z) and half sizes. A US size 7 is approximately UK size N or O. The conversion is not exact because the systems evolved independently.