Tiffany & Co, a famous jewelry company, sells a wide variety of rings including engagement, wedding and casual rings. If another person purchased a ring as a gift for you, there is a chance that the ring will not fit your finger properly. Like many premium jewelry stores, your local Tiffany & Co store may resize your ring for free. If the store will not resize your ring, or you don't have the receipt, you can take the ring to a jeweler along with a Tiffany's size chart.
Visit the Tiffany store where your ring was purchased. In many cases, the store will measure your finger and resize your ring for free. If they won't resize the ring, you will have to take it to an independent jeweler.
Measure your ring finger using a measuring tape. Determine the circumference of your finger in millimeters. Measure in the evening, when your finger is widest, on a day when you are not particularly bloated or dehydrated.
Print out the Tiffany ring size chart, see the resources section.
Using the measurement from the tape measure, determine your ring size using the size chart. If your measurement is between two sizes, you are a half size. For example, if your ring size is between 5 and 6, your are a size 5.5. Also determine the size of your ring on the size chart. Determine if the ring is too small or large.
Take your ring, and the Tiffany size chart, to a jeweler and tell him you want to resize the ring. Explain the current and desired size of the ring. In many cases, a jeweler will remeasure your finger and ring to double-check the size.