I'm a dismal failure at "doing the math", so can someone please answer this for me? I need curtain rings (the kind with the little loop on the bottom for drapes to hook into). I took a measuring tape and wrapped it around my curtain rod to get 4.25". What diameter ring should I use? (I know, I know ... idiotic, and I should know this!)

These are the drapes I'm getting shown in the seller's setting.