I would call this a Size Small to Medium, in order for the seams to line up over the hips properly, with ample room in the back for coverage. I'm a Small with a 26.5 inch waist and 37 inch hip. There is definitely about an inch of room all around for this to open up in size without changing the shape too much. It is meant to sit at your true waist so just at your belly button or above slightly. Basically the smallest point of your waist.

The length is a lovely midi-length (just below the knee and above the mid calf). The denim is a lovely vintage medium toned blue. Love the pocket details and just simple apron wrap style. So easy to wear and goes with pretty much anything. A staple piece of vintage to have in your wardrobe. In excellent vintage condition.

As usual please refer to the below measurements for most accurate fit.

Measurements: Laying Flat / Not Doubled / Not Stretched
These measurements are of the skirt closed up with the seams sitting at a true hip position.

Waist width: 13.75 inches wide
Hip width at bottom of pocket: 19 inches wide
Overall Length: 29.75 inches long