You can measure your ring size using either string or perhaps a more common item in your home floss. To find your ring size wrap a flexible measuring tape around the widest part of your finger near the knuckle.
Then line that up with a ruler and take down its length in millimeters.
How to know your ring size. Start by cutting out a strip of paper that is approximately 3 4 inch wide and 4 inches long. Print the ring sizer making sure that it is printed to actual size. One of the easiest ways to assess your ring size is to measure your finger with a strip of paper or string.
Wrap the paper around the base of the intended finger and then mark where the paper overlaps. With the numbers facing out slip the tip of the ring sizer through the slot. Aim for a snug but comfortable fit and make sure to measure the exact finger where you plan to wear the ring since even the same finger on different hands can be different sizes.
Place the sizer on your ring finger and carefully pull taut to read the finger size. Take one of these measurement tools and wrap it around the base of your finger marking where the string or floss first overlaps with a pen. Cut out the ring sizer and open the slot where marked.