The fingers of the left and right hand are often different in width. Please calculate your ring size on the hand where you will wear the ring.
Fingers are usually thinner in winter than in summer. The lower the temperature, the thinner the fingers.
The circumference of your fingers changes over the course of your life, so you shouldn’t rely on ring sizes measured a long time ago. Determine your ring size as directly as possible before purchase.
The size of the finger also changes often during the day. So the fingers in the morning are usually thinner than in the evening.