Road bike handlebar width ranges from 360mm to 460mm, typically matching 85–110% of shoulder width. Narrower bars (380–400mm) reduce drag and improve aerodynamics; wider bars (420–440mm) enhance breathing capacity and control. The trend over the past decade has shifted toward narrower bars — from industry averages of 44cm down to 40–42cm — reflecting advances in frame geometry and aerodynamic design. Your ideal width balances your shoulder structure, riding position, and the distances you target.