The size chart is based on the inner circumference of the stretch bracelets. To find your ideal size, measure your wrist with a soft tape measure or string. For a snug fit, add about ¼ inch (0.6 cm). For a looser fit, add about ½ inch (1.3 cm). Because these bracelets stretch, avoid adding more than ½ inch (1.3 cm) to ensure they stay comfortably secure.