Area Code 720 – Colorado
The phone area code for Colorado is 720 (international format +1720). Browse local exchange codes (NXX) and carrier assignments below.
📞 Exchange Codes (NXX) for Area Code 720
Select a central office code to view local carrier data and detailed information
📍 Geographic Location of Colorado
Overview of Area Code 720
Area code 720 is a geographic North American Numbering Plan Area (NPA) code serving the state of Colorado, United States. It functions as an overlay for the Denver metropolitan area and much of the Front Range urban corridor. Specifically, 720 overlays area code 303, which was one of the original 86 area codes assigned in 1947. The overlay was introduced on June 1, 1998, to provide additional numbering resources for the rapidly growing region. Today, 720 and 303 serve the same geographic area, requiring ten-digit dialing for all local calls within the region.
Geographic Coverage and Jurisdiction
The 720/303 overlay covers a large portion of north-central Colorado, including the cities of Denver, Boulder, Aurora, Lakewood, Centennial, Arvada, Westminster, and Golden. It also extends to several surrounding counties such as Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson. This area is the economic and population hub of Colorado, home to over 3 million residents. The overlay does not alter the geographic boundaries; rather, it adds an additional area code to the same region, ensuring sufficient numbering capacity for new telephone lines, mobile devices, and data services.
Dialing Formats and Caller Instructions
For local calls within the 303/720 region, callers must dial the full 10-digit number: the three-digit area code followed by the seven-digit subscriber number. For example, to call a landline in Denver from within the same area, dial 720-555-0123. For calls from outside the 303/720 region but within the United States, dial 1-720-555-0123. International callers should dial their country's exit code, then 1-720-555-0123 (e.g., from the UK: 00-1-720-555-0123).
Numbering Administration and Technical Notes
The 720 area code is administered by the Colorado Public Utilities Commission and the North American Numbering Plan Administrator (NANPA). It supports both wireline and wireless services, and number portability is fully implemented, meaning customers can retain their numbers when switching carriers. The overlay has eliminated the need for seven-digit dialing, and all calls within the region must be dialed as ten digits. This is a standard practice in overlays to avoid confusion and ensure correct routing.
Impact on Businesses and Residents
For businesses, having a 720 number can signal a local presence in the Denver metro area, which is beneficial for customer trust and local SEO. Residents and businesses alike should ensure their contact information reflects the correct area code and that all stored numbers use the ten-digit format. As the region continues to grow, additional overlays may be introduced in the future, but for now, 720 remains a vital part of Colorado's telecommunications infrastructure.