Area code lookup
303 area code
- State
- CO
- Cities covered
- 2
- Counties
- 2
- Time zone
- Mountain Time
Quick answer
Area code 303 serves Aurora and Denver in Colorado. It sits in Mountain Time and covers 2 counties and about 21 ZIP codes across the metros we track. Numbers there are also dialled as 720.
Cities in the 303 area code
Each city links to its full local profile: sales tax, housing, income and ZIP codes.
| City | County | Time zone | ZIP codes |
|---|---|---|---|
| Aurora, CO | Arapahoe County | MST/MDT | 9 |
| Denver, CO | Denver County | MST/MDT | 12 |
Related area codes
Codes that share or border the same calling area.
303 area code FAQ
The questions people ask about this code.
Where is area code 303?
303 is a geographic area code in Colorado, covering Aurora and Denver.
What time is it in the 303 area code?
303 observes Mountain Time (MST/MDT).
Is 303 a scam area code?
No — it is a normal geographic code, not a toll-free or premium-rate prefix. Caller ID can be spoofed on any code, so verify unexpected callers before sharing information.
Sources & transparency
- North American Numbering Plan Administrator (NANPA) area code assignments — area code to geography mapping and overlay relationships
- US Census Bureau, American Community Survey 2019-2023 5-year estimates — city, county and ZIP code geography
Last reviewed August 2026. Figures are published for reference and can change; verify with the source agency before filing or contracting. How we build and check this data.