303 Area Code — Colorado

303 is a North American Numbering Plan area code for Colorado, the United States. It covers about 3,294,473 people in 53 towns and 189 ZIP codes, including Denver, Aurora and Littleton.

Where area code 303 is used

Area code 303 is assigned to Colorado, the United States, inside the North American Numbering Plan. Numbers in the code are written (303) NXX-XXXX at home and +1 303 NXX-XXXX when dialled from outside Canada and the United States. Since the NANP moved to 10-digit dialling you must always include the area code, even for a local call.

Other area codes in this footprint: 720, 983. They serve towns in the same territory, so a single street can contain numbers from more than one code. That is normal in the NANP and does not change how you dial.

Towns and cities in area code 303

The 53 towns below are the largest in the 303 footprint, ranked by population. Every one of them links to its own page with the full list of area codes and ZIP codes for that town.

Counties covered

Other area codes serving the same towns

Nearby area codes

How to dial area code 303

• Within North America: 303 + 7-digit number (303-NXX-XXXX). The leading 1 is optional on a mobile phone and required on most landlines for long-distance.
• From abroad: your country's international prefix, then 1, then 303, then the 7-digit number — for example 00 1 303 NXX-XXXX from most of Europe.