303 Area Code
Covers Denver and nearby communities in Colorado.
(303) 555-0142Area code 303 map
Interactive coverage map for area code 303, centered on Denver, Colorado
39.7392, -104.9903
Open in OpenStreetMapArea code 303 coverage map — centered on Denver. Shaded area shows the approximate reach around the primary city.
Calls tagged with area code 303 come from Denver and nearby communities in Colorado. It reaches roughly 2.9 million people across places such as Denver, Aurora, Boulder, Lakewood and more. The region observes Mountain time, so a number like (303) 555-0142 is on that clock right now. Colorado's original 1947 code, now anchoring the Denver metro and overlaid by 720 and 983. It shares its territory with the overlay codes 720, 983, which sit on the exact same map. Because the 303 region uses more than one area code, you must dial all ten digits — area code included — even for a local call. You do not, however, need to dial a leading 1 for calls within the US and Canada. On this page you'll find a live local clock for Denver, an interactive coverage map, the cities and counties 303 serves, its overlay and neighboring codes, and tips on spotting 303 spam calls.
Cities covered by 303
Cities & neighborhoods
- Denver
- Aurora
- Boulder
- Lakewood
- Arvada
- Westminster
- Littleton
Counties
- Denver County
- Arapahoe County
- Jefferson County
- Adams County
- Boulder County
Looking for the broader picture? See all Colorado area codes.
Nearby & overlay area codes
Overlay codes (same area)
These share 303’s geography — a number in either code can be on the same street.
- 720Denver
- 983
Is a call from 303 a scam?
Because 303 covers a dense metro around Denver, it's a common source of both real business calls and spam. Legitimate 303 calls come from local businesses, offices and neighbors; scam calls in this region tend to imitate delivery services, banks and utilities. Remember that caller ID is trivially spoofed — a scammer anywhere can make a 303 number appear on your screen — so the area code alone never proves a call is genuinely local.
Red flags to watch for
- Pressure to act right now, or threats of arrest, fines, or service being cut off.
- Requests to pay with gift cards, wire transfer, crypto, or a payment app.
- Asking for passwords, one-time codes, your SSN, or full card/bank numbers.
- A robocall or recording, or a number that won’t let you call back.
When unsure, hang up and call the organization back on a number you look up yourself.
Calling a 303 number from abroad
Every 303 number is a US/Canada +1 number. From a mobile anywhere, the simplest approach is to dial it in international format:
+1 303 555-0142If your phone can’t dial the +, replace it with your country’s exit code, then 1, then the number:
- UK, Germany, France & most of Europe
00 1 303 555-0142 - Australia
0011 1 303 555-0142 - Japan
010 1 303 555-0142 - Mexico
00 1 303 555-0142
Within the US and Canada you don’t need any of this — just dial the ten digits 303 555-0142.
Reverse phone lookup
Check any US or Canada number to see whether it's a working line, which carrier it sits on, whether it's mobile, landline or VoIP, and roughly where it's registered.
Shows carrier, line type and location. Owner name isn't available here.
Results are for personal, informational use only and may not be used for employment, credit, housing or tenant-screening decisions.
Area code 303: frequently asked questions
Where is the 303 area code located?
The 303 area code is located in Colorado, centered on Denver. It covers Denver County, Arapahoe County, Jefferson County, Adams County, Boulder County and nearby communities including Denver, Aurora, Boulder, Lakewood, Arvada, Westminster.
What time zone is 303 in?
Area code 303 is in the Mountain time zone (UTC-7 (MST) / UTC-6 (MDT)). You can see the exact current local time for Denver on the live clock above.
What cities use area code 303?
Cities and areas that use 303 include Denver, Aurora, Boulder, Lakewood, Arvada, Westminster. Its primary city is Denver, CO.
Do I need to dial 1 before 303?
For calls within the US, you do not need to dial a leading 1, but you do need all ten digits: 303 plus the seven-digit number. The 303 area requires ten-digit dialing because more than one area code serves it.
Is 303 a toll-free or scam number?
No — 303 is a normal geographic area code for Denver, not a toll-free code (toll-free codes are 800, 833, 844, 855, 866, 877 and 888). A 303 number is not inherently a scam, but the code can be spoofed. See the spam-call section above for how to tell.
What are the overlay area codes for 303?
Area code 303 is overlaid by 720, 983, meaning those codes cover the same geographic area.