Area Code Overview

Area code 303 is a geographic telephone area code in Colorado that went into service on January 1, 1947. The geographic regions covered by this area code overlay has a population of approximately 967,697.

Overlay and Dialing Rules

Area Code: 303
State: Colorado
Type: General Purpose Code
In Service Date: January 1, 1947
Overlay Complex: 303/720/983
Local Dialing Plan: This area does require you to dial the area code when calling locally.

Estimated Number of Assigned Phone Numbers in Area Code 303

This area code is ranked 20th out of 363 nationwide in estimated assigned phone numbers. Within the state territory it serves, it is ranked 2nd out of 5.

6,943,000

Estimated Service-Type Mix of Assigned Phone Numbers in Area Code 303

Total assigned 6,943,000

Wireless

1,550,000 assigned

22.32%

Wireline and VoIP

4,757,000 assigned

68.52%

Other / Unclassified

636,000 assigned

9.16%

Estimated Share of Wireless Numbers Originally Assigned to Each Carrier in Area Code 303

Estimated assigned wireless phone numbers: 1,550,000

Numbers may later be ported to another carrier, but this chart reflects original number assignment, not current subscriber share.

Verizon Wireless 673,000 (43.42%)

AT&T Wireless 458,000 (29.55%)

T-Mobile 418,000 (26.97%)

ELBERT COUNTY WIRELESS, LLC 1,000 (0.06%)

Estimated Share of Wireline and VoIP Numbers Originally Assigned to Each Carrier in Area Code 303

Estimated assigned wireline and VoIP phone numbers: 4,757,000

Lumen 4,156,000 (87.37%)

Onvoy 218,000 (4.58%)

MCIMETRO ACCESS TRANSMISSION SERVICES LLC 165,000 (3.47%)

Comcast Business 77,000 (1.62%)

ELECTRIC LIGHTWAVE LLC DBA ALLSTREAM 43,000 (0.90%)

Spectrum 34,000 (0.71%)

Bandwidth 29,000 (0.61%)

PAETEC ITEL, LLC 17,000 (0.36%)

Commio 8,000 (0.17%)

TERRA NOVA TELECOM INC. 4,000 (0.08%)

Peerless Network 2,000 (0.04%)

AT&T 1,000 (0.02%)

Other / Unclassified Assigned Numbering in Area Code 303

Estimated assigned other or unclassified phone numbers: 636,000

SPOK, INC. 310,000 (48.74%)

TELEPORT COMMUNICATIONS AMERICA, LLC - CO 135,000 (21.23%)

AMERICAN MESSAGING SERVICES, LLC 110,000 (17.30%)

BIJOU TEL. COOP. ASSN., INC. 20,000 (3.14%)

COMMUNICATIONS UNLIMITED 20,000 (3.14%)

EASTERN SLOPE RURAL TEL. ASSN., INC. 10,000 (1.57%)

HD CARRIER LLC 10,000 (1.57%)

ROGGEN TEL. COOP. CO. 10,000 (1.57%)

AHOI LLC 4,000 (0.63%)

INTERLINK ADV SVC DBA FORETHOUGHT.NET - CO 3,000 (0.47%)

LIVE WIRE NETWORKS, INC. - CO 2,000 (0.31%)

EXIANT COMMUNICATIONS LLC 1,000 (0.16%)

Cities and Towns in Area Code 303

Allenspark, Colorado Bennett, Colorado Byers, Colorado Deckers, Colorado Deer Trail, Colorado Denver, Colorado Fort Lupton, Colorado Georgetown, Colorado Hudson, Colorado Keenesburg, Colorado Longmont, Colorado Roggen, Colorado Strasburg, Colorado

These geographic regions are also served by area codes 720 and 983.

How These Figures Were Built

These figures are estimates based on public phone-number assignment records. They are meant to show the likely mix of assigned phone numbers associated with area code 303, not live customer counts.

Some providers may have assigned phone numbers tied to this area code even if they do not actively market or sell service locally. These figures reflect public number-assignment records, not confirmed local service availability.

They also do not reflect number portability at the individual phone-number level, so some numbers may now be used on a different network or by a different provider than the original assignment records suggest.

Population data and locality matching provided by GeoNames.

Last refreshed: April 15, 2026 6:22 pm