For adolescents and teenage girls, ages 13 to 19, the average waist size is 32.6 inches. This is the equivalent of a medium or large pant size, or about a size 12.

And a size 8 dress of 1958 doesn't even have a modern-day equivalent — the waist and bust measurements of a Mad Men-era 8 come in smaller than today's size 00. Newsletter Daily Today’s Headlines ...

American women are on average between a misses size 16-18, or what is considered a plus-size 20W, according to a new study in the International Journal of Fashion Design, Technology and Education.

The physical characteristics of the 154 obese girls are shown in Table 1.The mean BMI was 27.4±3.8 (range 20.4–43.1); the mean waist circumference was 81.9±9.2 (range: 60–108).