For a quick size reference you need only find a quarter!
On a quarter, the characters of the text "IN GOD WE TRUST" are exactly 1mm tall. The characters of the text "UNITED STATES OF AMERICA" are 1.5mm tall. The quarter itself is 24mm dia which is just 1/16-in short of 1-inch.
We hope you can use this tip whenever you look at jewelry online!