If you don't have a ring sizer, cut a thin strip of paper, about 10-12cm long. Wrap the strip of paper tightly around your desired finger. Using a pen or a pencil, mark the point where the paper overlaps itself. Lay the strip of paper on a flat surface and use a ruler to measure the distance from the end of the strip to the marking you made, in millimeters. This will give you a measurement of the circumference of your finger. Using the below chart, convert your measurement into a standard US ring size. if you are in between two sizes, it is always best to round up rather than down.