Temperature Is Important
Don't measure when your body temperature is either too cold or too hot. A cold finger shrinks while a hot finger expands causing an inaccurate reading. Only measure when fingers are at room temperature.
When two sizes seem to fit
If you hesitate between two sizes, always go with the larger one.
A wider band needs a bigger size
If you consider purchasing a wide band, move up a size from your measurement, for comfort’s sake.
Don't use strings
When measuring your finger, always refrain from using a string, they tend to stretch, which can result in wrong size. ALWAYS use a paper strip about 1/2" in width.
Big knuckles can affect your size
If your knuckle is a lot larger than the base of your finger, measure both the base of your finger and your knuckle and select a size in between the two.
For best results, use a plain band
Extra wide band styles tend to run slightly small. If you're borrowing a ring for sizing and it has a narrower shaft than the one you wish to purchase, you may wish to order a ring a size larger than the normal size worn. Also, large stone rings may cause the shank to lift up when laid on its side on the display, slightly distorting the size measurements.
Is there a difference between sizes for men and for women?
No: ring sizes range in a continuous scale used for both men and women.