Proper fit makes all the difference:
Measure: Use flexible tape around your wrist where you'd wear the
bracelet.
Add room: For chain bracelets, add 0.5" (snug) to 1" (comfortable) to your measurement.
Bangle sizing: Measure around your closed hand at its widest point.
Average sizes: Women typically wear 6.5-7.5". Men typically wear 7.5-9".
Adjustable options: Cuffs and some chains offer flexibility in sizing.
When in doubt, slightly larger is better than too tight.