What size cinch do I need?

Hi All, just come across this forum for the first time. I used to ride Western years ago but sold all my tack to begin riding English. Now I have decided that I would like to start Western riding again. I have seen a saddle that I would like to buy, but need to buy a cinch. My Mare is ridden in an english girth measuring 46" but can't remember what size cinch I used to ride her in - can anyone help? Thank you