Colorado Area Codes

About Area Codes in Colorado

Colorado (CO) is the The Centennial State, located in the West region of the United States. With a 2023 population of 5,839,926 residents, Colorado is served by 4 active area codes. The state capital is Denver and the largest city is Denver.Colorado's official motto is "Nil sine Numine."

Area code assignments in Colorado follow the North American Numbering Plan (NANP), which has been in effect since 1947. As the state's population and demand for phone numbers grew — driven by the rise of cell phones, fax machines, pagers, and VoIP lines — regulators either split existing area codes geographically or added overlay codes that share the same territory. That's why Colorado now has 4 codes: 303, 719, 720, 970.

When you receive a call from a Colorado number, the area code tells you only where the number was originally assigned. Because of Local Number Portability (LNP), which took effect in 2003, callers can keep their phone numbers even when moving across state lines. So while a 303 number was once assigned in Colorado, the person calling you could be anywhere in the US today.

Time zones in Colorado

Colorado observes the Mountain time zone. Daylight Saving Time is observed from the second Sunday in March through the first Sunday in November, when clocks shift forward by one hour. When you call a Colorado number from outside the state, double-check the local time above each area code detail page to avoid calling at unreasonable hours.

Phone number format in Colorado

All Colorado phone numbers follow the standard 10-digit NANP format: (NPA) NXX-XXXX. For local calls within Colorado, you typically need to dial the full 10-digit number — even for calls within the same area code — because of mandatory 10-digit dialing imposed by the FCC for areas with overlay codes (most of Colorado's territory). For long-distance calls within the NANP, dial 1 + area code + 7-digit number.

Frequently asked questions about Colorado area codes

How many area codes does Colorado have?

Colorado currently has 4 active area codes: 303, 719, 720, 970.

What is Colorado's original area code?

The oldest area code(s) in Colorado were assigned in 1947 as part of the original 86 NANP codes. These legacy codes typically covered the entire state at first, then were split as demand grew.

What time zone is Colorado in?

Colorado is in the Mountain time zone.

Will Colorado get more area codes?

As Colorado's population and number demand grow, NANPA may assign additional overlay codes. When the current codes run out of available prefixes, regulators announce public hearings and propose new codes. The AreaCodeCentral team tracks these announcements and updates the directory within 24 hours of any new code activation.