Measuring Ring Size
Go to a professional goldsmith or jewellery store. The ring must slide on then be a tug to come off.
If you are wanting a wide band ring make sure to be measured by wide band sizers. Or a narrow ring, narrow ring sizers.
Your finger size may fluctuate depending on the season. Slightly larger during the heat of the summer, and slightly smaller in the cold of winter.
It's always best practice to have your finger sized several times.
A perfect fit is when the ring slides on and pops into a pocket then requires a tug to come off.