Cities in area code 303
303 numbers are anchored to 13 rate centers across Colorado. Each row shows how many active prefixes the locality holds — a direct measure of its numbering footprint.
Denver, Longmont, Fort Lupton, Deckers, Keenesburg, Hudson, Georgetown and Deer Trail hold the largest prefix inventories; and 4 smaller communities down to single-prefix localities. Each locality below links to its rate-center page with the full prefix list.
Metropolitan coverage: 8 rate centers belong to FCC top-100 metro areas.
Overlap note: 13 localities are shared with other area codes, so a neighbor's number may differ in its first three digits.
Clock-wise the coverage is Mountain.
A caller's real location can differ: numbers port between carriers and follow their owners when they move. Use the prefix tables to see where a specific number block was issued.
| Locality (rate center) | Active prefixes | Metro area | All codes serving it |
|---|---|---|---|
| Denver | 735 | Denver-Aurora-Centennial, CO | 303, 720, 983 |
| Longmont | 18 | — | 303, 720, 983 |
| Fort Lupton | 11 | — | 303, 720, 983 |
| Deckers | 5 | Denver-Aurora-Centennial, CO | 303, 720, 983 |
| Keenesburg | 3 | Denver-Aurora-Centennial, CO | 303, 720 |
| Hudson | 2 | — | 303, 720 |
| Georgetown | 2 | Denver-Aurora-Centennial, CO | 303, 720 |
| Deer Trail | 2 | Denver-Aurora-Centennial, CO | 303, 720 |
| Allenspark-lyons | 2 | — | 303, 720 |
| Strasburg | 1 | Denver-Aurora-Centennial, CO | 303, 720, 983 |
| Bennett | 1 | Denver-Aurora-Centennial, CO | 303, 720 |
| Byers | 1 | Denver-Aurora-Centennial, CO | 303, 720 |
| Roggen | 1 | — | 303, 983 |
FAQ
What is the biggest city in area code 303?
Denver holds the most active prefixes (735), making it the code's largest numbering locality.
How many places does 303 cover?
13 rate centers in Colorado hold active 303 prefixes, from Denver down to communities with a single prefix.
Does a 303 number guarantee the caller lives in one of these places?
No — the tables show where number blocks were issued. Porting and VoIP let people keep or acquire numbers anywhere.