303 Area CodeDenver, CO
Area code 303 covers Denver and nearby communities in Colorado, in the Mountain Time (MT) zone, home to about 3.2 million people across 137 cities. It overlays 720, so the same region uses both and every local call needs all ten digits.
Overview
- Major City
- Denver
- State
- Colorado (CO)
- Timezone
- Mountain Time (MT)
- Current Time
- Overlay
- Yes – shares area with 720
Where is area code 303?
Area code 303 serves part of Denver, CO and the surrounding areas. It has a single overlay (720) that serves the same area.
Overview of the 303 Area Code
What is the 303 area code?
The 303 area code serves Denver, Colorado, alongside other established area codes. When you see a 303 number, it indicates a local number within this geographic area.
Why was area code 303 created?
The 303 area code was introduced as an overlay to add numbers in Denver once the existing area code 720 began to run out of available prefixes. It added a new supply of numbers without requiring current residents to change their existing digits.
Geographic Coverage of the 303 Area Code
The 303 area code serves Denver and surrounding areas in Colorado. It operates within the Mountain Time (MT) time zone. It complements the coverage of area code 720. This area code covers several key cities, including:
- Denver
- Aurora
- Lakewood
- Thornton
- Arvada
- Westminster
Got a call from a 303 number? It came from Denver, CO. Since 303 overlays with 720, every local call in the region needs all ten digits to land on the right line. Inside 303, Denver holds about 23% of the population; the rest is split across 136 smaller cities.
Denver Area Codes Overview
Denver is served by multiple area codes, reflecting its telecommunications needs. The 303 area code operates alongside 720. Here are the area codes serving this region:
The introduction of the 303 area code helped prevent number exhaustion, ensuring a continuous supply of phone numbers across the geographic area.
What cities does area code 303 cover?
| City | State | Population | % of Area Code | % of City |
|---|---|---|---|---|
| Denver | CO | 729,019 | 2% | 100% |
| Aurora | CO | 403,130 | 2% | 100% |
| Lakewood | CO | 156,868 | 1% | 100% |
| Thornton | CO | 146,689 | 1% | 100% |
| Arvada | CO | 121,873 | 1% | 100% |
| Westminster | CO | 115,302 | 0% | 100% |
| Centennial | CO | 108,853 | 0% | 100% |
| Boulder | CO | 106,803 | 0% | 100% |
| Longmont | CO | 99,818 | 0% | 100% |
| Highlands Ranch | CO | 96,713 | 0% | 100% |
* Sources: Population – U.S. Census Bureau PEP, Vintage 2024 (SUB-IP-EST2024-POP). Area code assignments – NANPA CO Code data. See our data methodology.
Has area code 303 been reported for unwanted calls?
Yes – 1,109 unwanted-call complaints were reported to the FTC for numbers showing a 303 area code (May 29 – Jul 2, 2026).
- 60% robocalls
- ↑ 5% vs prior period
Most-reported subjects
- Other53%585
- Home improvement & cleaning14%152
- Medical & prescriptions11%124
* Caller ID is easily spoofed, so these figures reflect the number shown on caller ID, not the caller's true location – an area code alone never identifies a caller. The FTC does not verify the facts in these complaints. Source: FTC Do Not Call (DNC) Reported Calls Data, retrieved 2026-07-05.
Which prefixes and exchanges belong to area code 303?
78% assigned to a telco
- 79% Landline
- 21% Wireless
- 0% Unknown
| Prefix | Usage | Carrier |
|---|---|---|
| (303)200- | Landline | Teleport Communications America |
| (303)201- | Wireless | Usa Mobility Wireless |
| (303)202- | Landline | Qwest |
| (303)203- | Landline | American Messaging Services |
| (303)204- | Wireless | Verizon Wireless |
| (303)205- | Landline | Qwest |
| (303)206- | Wireless | Usa Mobility Wireless |
| (303)207- | Wireless | Usa Mobility Wireless |
| (303)208- | Wireless | Usa Mobility Wireless |
| (303)209- | Landline | Mcimetro Access Transmission Services |
Frequently Asked Questions about the 303 Area Code
Who called me from a 303 number?
A 303 number is assigned to Denver, Colorado, so a call may come from there. But caller ID is easy to fake, and scammers often spoof a local 303 code to look nearby, so a 303 number doesn't prove the caller is local. Recently, 1,109 unwanted-call complaints were reported to the FTC for numbers showing the 303 code (60% flagged as robocalls). If you don't recognize the number, let it go to voicemail; a real caller will leave a message.
Is 303 a scam area code?
No area code is a scam on its own. 303 is a normal, officially assigned code for Denver, Colorado. Spam callers spoof local codes to raise the odds you answer, so 303 on your caller ID says nothing about who is really calling. Recently, 1,109 unwanted-call complaints were reported to the FTC for numbers showing the 303 code (60% flagged as robocalls). Judge the call itself, not the area code.
Why do I keep getting calls from the 303 area code?
Repeated calls from different 303 numbers are usually spoofing: a robocaller rotates through 303 numbers so each call looks local and slips past simple blocks. Recently, 1,109 unwanted-call complaints were reported to the FTC for numbers showing the 303 code (60% flagged as robocalls). Blocking one number rarely helps; voicemail screening, your carrier spam filter, and the Do Not Call Registry work better.
Should I answer an unknown 303 number?
If you aren't expecting a 303 call, let it ring to voicemail. Legitimate callers leave a message, most robocallers hang up when no one picks up, and answering can mark your number as active and bring more calls.
How do I block calls from the 303 area code?
Block a single 303 number from your recent-calls list (iPhone: tap the number, then Block this Caller; Android: tap the number, then Block or report spam). To cut the volume, turn on Silence Unknown Callers on iPhone or spam protection on Android, enable spam filtering from your carrier, and register at DoNotCall.gov. Blocking the entire 303 code also stops legitimate local calls, so use it only as a last resort.
Where is area code 303?
Area code 303 covers Denver and the surrounding area in Colorado, spanning 137 cities with about 3,173,465 residents. It shares its area with overlay code 720.
Is 303 a real area code?
Yes. 303 is an active code in the North American Numbering Plan, assigned by NANPA and in service for Denver, Colorado. A real code can still show up on spoofed spam calls, so treat unknown 303 calls with normal caution.
What timezone is the 303 area code in?
The 303 area code is in the Mountain Time (MT). Because a number can be kept when someone moves or switches to VoIP, a specific 303 caller may not be in that zone.
How do I call a 303 number from abroad?
From outside the US, dial your country's exit code, then 1 (the US country code), then 303 and the seven-digit number. From a mobile phone you can usually just enter +1 303 followed by the number and let the phone add the exit code for you.