are ring sizes in millimeters?
Option one: Use string or floss to measure your finger You can measure your ring size using either string or, perhaps a more common item in your home, floss. ... Common ring sizes for women are 6 (16.5 mm), 6.5 (16.9 mm), and 7 (17.3 mm). For men, the most common sizes are 10 (19.8 mm), 10.5 (20.2 mm), and 11 (20.6 mm).