Bikini Size Calculator

Swimwear is fitted from four circumferences because the top and the bottom are sized by different parts of the body. Bust circumference at the fullest point sets the top; hip circumference at the widest point sets the bottom; and when an underbust measurement is supplied, the difference between bust and underbust gives cup depth on the familiar one-inch-per-cup scale, so a 4 inch difference reads as a C cup. Because the two garments are sized independently, mismatched pairs are ordinary rather than exceptional: a 34 inch bust with 42 inch hips genuinely calls for a small top and an extra large bottom, which is exactly why mix-and-match sizing exists. The waist-to-hip ratio is reported here as a shape descriptor, not a health measure; values below about 0.75 read as a defined waist, while values above 0.85 read as a straighter line through the torso. The size bands follow common US ready-to-wear practice, but the underlying body measurement tables come from voluntary documents such as ASTM D5585 and ISO 8559, and no brand is obliged to follow them, so real-world variation of one to two sizes between labels is normal. Fabric adds a further variable: swim knits with 15 to 20 percent elastane can stretch well over half again their relaxed width, which means fit depends on the garment's unstretched dimensions and recovery, not on body measurement alone.

The two-piece swimsuit predates its name, appearing in Mediterranean beachwear and Hollywood costume during the 1930s, but the modern garment dates precisely to the summer of 1946. The French engineer Louis Reard presented a minimal four-triangle design in Paris on 5 July 1946 and named it the bikini after Bikini Atoll, where the United States had begun nuclear testing days earlier; the couturier Jacques Heim had launched a rival two-piece called the Atome shortly before. Adoption was slow and contested, with bans in several countries, and the style only became mainstream across Europe and North America through the late 1950s and 1960s. Sizing has a separate and messier history. American ready-to-wear numbering derives from a survey of roughly 15,000 women conducted between 1939 and 1940 under the Works Progress Administration, which was turned into the voluntary Commercial Standard CS 215-58, issued in 1958 and later reissued as a Product Standard. The federal government withdrew it in 1983, removing the common reference point and opening the way to the label-by-label drift usually called vanity sizing. Since then the technical work has rested with voluntary bodies: ASTM International publishes body measurement tables such as D5585 for women's figures, ISO 8559 defines the measurement procedures themselves, and three-dimensional body scanning surveys from the early 2000s onward have supplied updated population data.