A size 28 in jeans for women equals a size 6, or a measurement of 28 inches at the pant's waist. For men, a size 28 equals a waist measurement of 29 3/4 inches.
Sizing for women's denim is fairly simple; the measurement of the waist of a pair of jeans equals the size's number. For example, a 28 always means a pant measures 28 inches at the waist. Women's denim can also be sized in even numbers staring at 0 and continuing upward.
For men, denim sizing is slightly different, as the natural waistline for men falls at a different point than for women. Refer to the denim sizing chart of your favorite brand to learn more.