Newmarket, NH is currently using only one area code which is area code 603. Area code 603 covers the entire state of New Hampshire and was established in 1947.
In addition to Newmarket, NH area code 603 serves the larger cities and communities of Amherst, Concord, Derry, Dover, Keene, Manchester, Nashua, Portsmouth and Rochester in addition to many smaller communities within the service area.
Newmarket, NH is located in Rockingham County and observes the Eastern Time Zone. View our Times by Area Code tool.