This guide is for general information only and is not legal advice. Laws change — verify current rules with your state DOT or a licensed attorney before relying on this for any legal matter. Read full disclaimer.
New Hampshire requires a bicycle helmet for any rider under the age of 16. The same rule extends to children carried as passengers in a child seat or trailer. RSA 265:144 requires every operator and passenger under 16 to wear a properly fitted helmet that meets ANSI, Snell, or ASTM standards on any public way, public bicycle path, or other public right-of-way. The first offense is a warning; subsequent offenses carry a fine of up to $25, which a court may waive on proof of helmet purchase. See RSA 265:144 (Bicycle helmets).
If you're 16 or older, New Hampshire doesn't require you to wear a helmet by state law. Riders under 16 (and any child carried as a passenger) must wear a helmet that meets the ANSI Z90.4, Snell, or ASTM (a CPSC-certified helmet meets these specifications) standard.
Cities can be stricter than the state floor, and bike-share systems often require helmets regardless of age. If you're renting or commuting in a major city, confirm the local rule before you ride.