Ring Sizing
For the best ring size measurement I would strongly advise that you go to a reputable jeweller and ask to have the finger correctly measured using a metal ring measurer.
If this is not possible you can buy cheap ring sizers from amazon (ring sizer), these are not as accurate as ones jewellers use but give a better idea - these ring sizer tools work better than paper and string which can both stretch—causing an inaccurate measurement.
The final option is to measure the inside diameter of an existing ring and compare it to the ring sizing chart below:
If you do decide to measure your finger please follow the tips to ensure your measurement is as accurate as possible:
be sure the finger is at normal or slightly elevated body temperature, as fingers shrink and expand when hot or cold
the best time for the most accurate sizing is near the end of the day when the fingers are warm
when the hands are cold, like they often are in the morning, the fingers will measure smaller
measure the finger three to four times to prevent inaccuracies
left-hand and right-hand ring fingers can differ in size
If the knuckle is noticeably larger than the base of your finger, record both measurements and choose a ring size that’s in-between the two
the ring should slide over the knuckle, but shouldn’t be so loose that you’ll risk having it slip off or move around excessively
the ring should fit snugly over the knuckle to prevent the ring from falling off, it shouldn’t be too tight, though, otherwise blood flow may be restricted
wider bands (those 6mm or wider) tend to fit more snugly than other styles, maybe order a quarter to a half size larger