1.Get a ring that fits you comfortably, not too loose (preferably a standard size band, not a thick ring)
2. Get a ruler and measure from one side of the ring to the other side (inside circle only)
3. Place the ruler in the middle of the circle to work out how many millimeters the inside hole of your ring is
4.Please refer to photo below;
For example this photo shows that the inside of the ring hole is approx. 18mm wide, which equates to a size 57.
Here are our ring size chart to find the perfect ring size for your finger: