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Colorado Area Codes

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State: Colorado (CO)
Area Codes: 4
Timezone: Mountain (MDT)
Current Time: 9:22 PM

About Colorado Area Codes

Colorado (CO) uses 4 telephone area codes to serve its residents and businesses. With an estimated population of 7,734,597, Colorado is one of the smaller states in the North American Numbering Plan (NANP). The state is primarily in the Mountain Time Zone (MDT). The current local time in Colorado is 9:22 PM.

The largest cities in Colorado include Denver (pop. 2,876,625), Colorado Springs (pop. 642,413), Aurora (pop. 379,289), Fort Collins (pop. 312,666) and Lakewood (pop. 157,935) . Colorado has 64 counties spread across its territory. Each area code in CO covers a geographic region of the state, with some areas using overlay codes that share the same geographic territory as an existing area code.

When calling a Colorado phone number from outside the area code, you must dial the full 10-digit number: the 3-digit area code followed by the 7-digit local number. Many parts of Colorado now require 10-digit dialing even for local calls due to overlay area codes and the nationwide 988 Suicide & Crisis Lifeline implementation.

All Colorado Area Codes

The table below lists every active area code in Colorado, along with the major city served and other cities covered by each code.

Area Code Major City Other Cities
303 Denver Aurora, Fort Collins, Lakewood, Boulder, Arvada, Westminster, Centennial, Longmont and more
719 Denver Colorado Springs, Lakewood, Pueblo, Fountain, Cañon City, Woodland Park, Alamosa, Trinidad and more
720 Denver Aurora, Fort Collins, Lakewood, Boulder, Arvada, Westminster, Centennial, Longmont and more
970 Denver Colorado Springs, Aurora, Fort Collins, Lakewood, Grand Junction, Greeley, Centennial, Loveland and more

Largest Cities in Colorado

These are the largest cities in Colorado by population, along with their primary area codes and counties.

City Population County
Denver 2,876,625 Denver County
Colorado Springs 642,413 El Paso County
Aurora 379,289 Adams County
Fort Collins 312,666 Larimer County
Lakewood 157,935 Jefferson County
Pueblo 143,932 Pueblo County
Thornton 141,464 Adams County
Grand Junction 139,143 Mesa County
Greeley 137,810 Weld County
Boulder 124,345 Boulder County

Frequently Asked Questions

Colorado has 4 active area codes. These include 303 (Denver), 719 (Denver), 720 (Denver) and 970 (Denver) .

Colorado is primarily in the Mountain Time Zone (MDT). The current local time is 9:22 PM.

The area code covering the most cities in Colorado is 970, which serves Denver and 122+ other communities.

Yes, most areas in Colorado now require 10-digit dialing (area code + 7-digit number) for all local calls. This requirement was implemented across the United States starting in October 2021 to support the 988 Suicide & Crisis Lifeline. Even if you are calling within the same area code, you need to dial all 10 digits.

To call a Colorado number from within the United States, dial the area code followed by the 7-digit phone number (e.g., 303-XXX-XXXX). From outside the US, dial your country's exit code, then 1 (the US country code), then the full 10-digit number.

Colorado has 64 counties. The state's total estimated population is 7,734,597, spread across these counties and served by 4 area codes.

Denver is served by area code 303. Colorado has 4 area codes in total — see the complete list above.
Colorado at a Glance
  • Abbreviation CO
  • Area Codes 4
  • Population 7,734,597
  • Counties 64
  • Cities 448
  • Time Zone Mountain
  • Current Time 9:22 PM
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