For shoes, measure foot length in centimeters and compare to the brand's size chart. When between sizes, choose the larger size for comfort.
For rings, wrap a thin strip of paper around the base of the finger, mark the overlap, and measure the length. This gives your circumference in millimeters.
Different regions label sizes differently. Use the conversion charts and double-check fit notes, especially for wider bands.
If you are gifting, adjustable styles or half sizes provide flexibility without sacrificing elegance.