Curtains

Ten years after moving into our house, we finally decided to trade the tired looking blinds in the living room and dining room for cozy curtains. First I went downtown to the fashion district, and purchased some lovely material. (see photo) Then, I did a lot of measuring of all the windows, and started sewing the curtains. Mr. Billett volunteered to pick out an order the curtain rods, rings and clips.
As he was looking for curtain rods online, he asked me how wide each panel was, so that he can figure out how many rings to get. The website we ordered from suggested four rings per foot. Unfortunately, I measured the curtains in centimeters, because I grew up in Hungary using the metric system, and feel more comfortable with it. When I told him the width of one panel was 230 cm, he had to do some math to figure out how many rings to order, keeping in mind that we will need two panels for one window. He did it, can you?