Boulder, Colorado Area Code
Boulder, CO utilizes an area code overlay in which area codes 303 and 720 serve the same geographic area. Ten digit dialing (area code + seven digit number) is necessary.
In addition to Boulder, CO area code information read more about area codes 303 and 720 details and Colorado area codes.
Boulder, CO is located in Boulder County and observes the Mountain Time Zone. View our Times by Area Code tool.