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US area code · Colorado

Area code 303

Where the 303 area code is, its overlay and how to dial a +1 303 number from anywhere.

CoversDenver, ColoradoTime zoneMountain (MT)TypeOverlay
Quick answer

The 303 area code is in Denver, Colorado, United States (Mountain (MT)). To call from abroad: +1 303 555-0123. It is an overlay, so all 10 digits are dialled.

StateColorado
Main areaDenver
Time zoneMountain (MT)
TypeOverlay
10-digit dialingRequired
In service since01-Jan-1947

The 303 area code is a geographic North American Numbering Plan (NANP) code covering Denver, Colorado. It has been in service since 01-Jan-1947 and sits in the Mountain (MT) time zone.

Overlay 303 shares its region

Several area codes cover the same geographic area, so two neighbours can have different codes. Because of the overlay, you must dial all 10 digits (area code + number) even for local calls.

303720983

How to dial a 303 number

From abroad+1 303 555-0123
Within the US / Canada1 303 555-0123
Locally (same area)303 555-0123

Cities in the 303 area code

A 303 number is usually in one of these places in Colorado — 12 counties.

Arvada JeffersonAurora Adams;ArapahoeBoulder BoulderBrighton Adams;WeldBroomfield Broomfield;JeffersonCastle Rock DouglasCastlewoodColumbineCommerce City AdamsDenver Adams;Arapahoe;Denver;JeffersonEnglewood ArapahoeHighlands RanchKen CarylLafayette BoulderLakewoodLittleton Arapahoe;Douglas;JeffersonLongmont Boulder;WeldLoveland LarimerNorthglennParker DouglasSouthglennThorntonWestminster AdamsWheat Ridge Jefferson

Other Colorado area codes

719720748970983

Frequently asked questions

Where is the 303 area code?

The 303 area code is in Denver, Colorado, United States (Mountain (MT)).

Is 303 an overlay area code?

Yes. 303 overlays the same region as 720, 983, so callers dial all 10 digits.

Do I have to dial 10 digits for 303?

Yes — dial the area code plus the seven-digit number.

How do I call a 303 number from another country?

Dial your exit code (or +), then 1, then 303, then the number: +1 303 555-0123.

Source: NANPA numbering plan. An area code covers a region, not a precise address — a 303 number does not pinpoint a street or ZIP code.

Missed a call from +1 303?

In the 30 days to September 24, 2026, 901 unwanted calls showing a 303 number were reported to the US Federal Trade Commission, 54% of them recorded messages or robocalls. That puts 303 at #55 of 670 area codes reported.

Other514
Dropped call or no message103
Medical & prescriptions82
Calls pretending to be government, businesses, or family and friends59
Before you call back
  • If you do not know anyone in Colorado, do not call back: a genuine caller will leave a message or send a text.
  • Scammers fake the number shown on caller ID, so a 303 number can hide a caller anywhere in the world.
  • Never give a code received by text or a bank detail to an unknown caller. In the US, calls can be reported at reportfraud.ftc.gov.

Who issues +1 303 numbers

Phone companies hold blocks of numbers in each area code. The main holders in 303:

Qwest Corporation 449Cellco Partnership Dba Verizon Wireless 60Level 3 Communications, LLC 58T-Mobile USA, Inc. 39New Cingular Wireless PCS, LLC 35Spok, Inc. 31

About 16.9% of the 800 prefixes in use belong to mobile carriers: a 303 number is often a cell phone, and it may have moved to another carrier since.

Sources: FTC Do Not Call reported calls (numbers as reported by consumers, not verified), NANPA central office code assignments.

All US area codes United States +1 Map of area code 303 — cities & rate centres