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Area code 303

Area code 303 Denver, Colorado

Area code 303 is one of the original 1947 area codes, in Colorado, with numbers assigned in Denver, Longmont, Fort Lupton and 7 more places. It’s 10:13 PM there now.

State
Colorado6 area codes in Colorado
Time zone
Mountain10:13 PM there now
Exchanges
78410 places
Overlay
720 and 983Same area, 10-digit dialing
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Where area code 303 is

Numbers in 303 are assigned to 10 places in 6 counties: Denver County, Weld County, Boulder County, Arapahoe County, Clear Creek County and Adams County.

Denver holds most of them: 94% of the exchanges.

  • Denver735
  • Longmont18
  • Fort Lupton11
  • Keenesburg3
  • Hudson2
  • Georgetown2
  • Deer Trail2
  • Strasburg1
  • Bennett1
  • Byers1

Phone companies in 303

784 blocks of numbers in 303 are held by 26 phone companies. The most belong to Lumen (CenturyLink) (448), Verizon Wireless (60) and Lumen (Level 3) (60).

Mostly landline: about 59% of blocks belong to local phone and cable companies, 17% to wireless networks and 24% to other carriers.

A block’s holder is the company it was first assigned to; numbers can move to other carriers since.

History and overlays

303 has been in service since 1947, when the first North American area codes were set up.

720 (since 1998) and 983 (since 2022) share the same area, so a new number there can get any of these codes and local calls are dialed with all 10 digits.

8 new exchanges were assigned since 2021, the latest in January 2025.

Calling 303

It’s 10:13 PM Mountain time in 303 right now.

From elsewhere in the U.S., dial 1, 303 and the 7-digit number; inside the area, all 10 digits too.

Nearby area codes

Colorado has 6 area codes: 303, 719, 720, 748, 970 and 983.

From the North American Numbering Plan Administrator’s area code and exchange records (10/22/2026) and U.S. Census place and county names. Places and companies are where number blocks were assigned, not where anyone lives or which carrier a number uses today.

Map of the 303 area code

Map of the 303 area code around Denver, Longmont and Fort Lupton, Colorado.

Interactive map © OpenStreetMap contributors

Cities on the map

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Questions about 303

Where is area code 303?

In Colorado, covering Denver, Longmont and Fort Lupton and other places across 6 counties.

What time zone is 303 in?

Mountain time. It was 10:13 PM there when this page loaded.

Is 303 an overlay?

Yes. 720 and 983 serve the same area, so dial all 10 digits for local calls.

Which phone companies have 303 numbers?

26 companies hold blocks; the most belong to Lumen (CenturyLink), Verizon Wireless and Lumen (Level 3). About 17% of blocks are wireless.

Is 303 running out of numbers?

Not on record. 8 new exchanges have been assigned since 2021.