Colorado Area Codes: Complete List With Cities Served
Colorado is served by 5 area codes. Several of them are overlays, which means two or more codes share the same territory.
Colorado area code list
| Area code | Main places served |
|---|---|
| 303 | Denver, Aurora, Littleton and Boulder |
| 719 | Colorado Springs, Pueblo, Limon and Usaf Academy |
| 720 | Denver, Aurora, Littleton and Boulder |
| 970 | Fort Collins, Grand Junction, Greeley and Steamboat Springs |
| 983 | Denver, Aurora, Littleton and Boulder |
Place names come from ZIP code records linked to each area code, so they show where a code is most common rather than exact boundaries.
Area codes by major city
| City | Area codes |
|---|---|
| Denver | 303, 720, 983 |
| Colorado Springs | 303, 719, 720, 983 |
| Aurora | 303, 720, 983 |
| Littleton | 303, 720, 983 |
| Pueblo | 719 |
| Grand Junction | 970 |
| Arvada | 303, 720, 983 |
| Boulder | 303, 720, 983 |
| Fort Collins | 970 |
| Englewood | 303, 720, 983 |
| Brighton | 303, 720, 983 |
| Broomfield | 303, 720, 983 |
| Castle Rock | 303, 720, 983 |
| Longmont | 303, 720, 970, 983 |
| Dinosaur | 970 |
How to format a Colorado phone number
US numbers have ten digits: the area code, a three-digit exchange and a four-digit line number. A Colorado number is written as (303) 555-0123 for display, or +13035550123 in E.164 format for storage.
Safe numbers for testing
The range 555-0100 to 555-0199 is reserved for fictional use in every area code. Our generator combines these with real local area codes, so test data looks right without reaching a real person.
Why overlays matter for your forms
With overlays, you cannot guess a city from its area code alone, and people who move keep their numbers. Use area codes for display and formatting, not for location checks.
Create realistic Colorado addresses for testing, with real cities, counties and ZIP codes.
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