Mine measured 12 inches. REMEMBER THIS NUMBER you will use it a few more times. Next I DOUBLED that measurement for my ruffles so I cut 24 inch strips of fabric in 3 inch wide sections. I used three of these for my bottoms.
2. With WRONG sides facing fold your fabric in half and sew a gathering stitch along the entire strip. Repeat with your other strips.
3. Pull your string to gather and make a ruffle. Gather to match your bottom measurement plus an inch for turning under to make a clean finish.
4. Pin your ruffle straight across the back of your bottoms. I found it was easiest to start at the bottom and work your way up. Sew it down. Don'f forget to tuck the ends under for a clean finish.