Area code
303
303 is a United States area code. Under the North American Numbering Plan it belongs to Colorado, which has 6 area codes in total.
Validate a number in 303
Paste a full number and the tool checks it against the numbering plan. It returns the standard formats, the line type the plan assigns and the area code region.
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Area code 303 at a glance
NANPA lists 784 central office codes (prefixes) in use in area code 303, held by 27 holders across 13 rate centers.
| Fact | Value |
|---|---|
| In service since | 1947-01-01 |
| Time zone | Mountain (M) |
| Assigned overlays | 720 (1998-06-01), 983 (2022-06-17) |
| Prefixes in use | 784 |
| Pooled prefixes | 228 (29%) |
| Rate centers | 13 |
| Companies holding prefixes | 27 |
| Assignment dates on file | 2001-04-12 to 2025-01-16 (37 prefixes) |
| ZIP codes in its places | 79 |
Rate centers in area code 303
The largest rate center is DENVER, with 735 prefixes (94%).
| Rate center | Prefixes | Share |
|---|---|---|
| DENVER | 735 | 94% |
| LONGMONT | 18 | 2% |
| FORTLUPTON | 11 | 1% |
| DECKERS | 5 | <1% |
| KEENESBURG | 3 | <1% |
| ALLNSPKLYN | 2 | <1% |
| DEER TRAIL | 2 | <1% |
| GEORGETOWN | 2 | <1% |
| 5 other rate centers | 6 | <1% |
Who holds the prefixes in 303
Qwest holds the most prefixes, 448 (57%). 29% of the prefixes are pooled, which means their thousands-blocks can belong to different companies.
| Holder | Prefixes | Share |
|---|---|---|
| Qwest | 448 | 57% |
| Verizon Wireless | 60 | 8% |
| Level 3 Communications | 58 | 7% |
| T-Mobile USA | 39 | 5% |
| New Cingular Wireless PCS | 35 | 4% |
| Mcimetro Access Transmission Services | 31 | 4% |
| 21 other carriers | 113 | 14% |
A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company. Find which carrier a number is on, or browse the prefix holders.
History of area code 303
- 1947-01-01 Area code 303 went into service.
- 1988-03-05 Area code 719 went into service and names 303 as its parent.
- 1995-04-02 Area code 970 went into service and names 303 as its parent.
- 1998-06-01 Area code 720 went into service as an overlay in the same area as 303.
- 2022-06-17 Area code 983 went into service as an overlay in the same area as 303.
Area codes nearest to 303
Distance is measured between the centers of the ZIP code places each area code serves, so it is a rough guide.
Overlay codes in the same area
ZIP codes in area code 303
79 ZIP codes fall in places that have a rate center in this area code.
| Place | ZIP codes |
|---|---|
| Denver, CO | 66 |
| Longmont, CO | 4 |
| Bennett, CO | 1 |
A ZIP code and an area code are unrelated systems. A ZIP code can sit in more than one area code, and an area code spans many ZIP codes.
Complaints on file for 303 numbers
6,982 FCC complaints are on file for 5,710 numbers in 303, most often filed as "Unwanted Calls". These are unverified consumer reports.
| Year of latest complaint | Numbers |
|---|---|
| 2023 | 197 |
| 2024 | 134 |
| 2025 | 195 |
Other area codes in Colorado
Colorado is one state with 6 area codes in the NANPA table. 303 is one of them.
Next to 303 in the numbering table
These are the codes just before and after 303 when all are sorted by number. They are neighbours on the list, not necessarily on the map.
What the area code does and does not tell you
A number that starts with 303 was first assigned in Colorado. That is a fact about where the number began, and it is a useful hint when you check a form entry, for example a billing address in Colorado next to a 303 phone number.
It does not show where the person is today. A number stays with its owner after a move or a change of provider (number portability), and mobile numbers travel with the handset. The area code also cannot tell you whether the line is active, who the carrier is, or whether the number is mobile or fixed: the plan shares those ranges. Read more about the area code, the numbering plan and line type.
Check numbers in bulk with the API
| Product | Credits | Docs |
|---|---|---|
| Phone Numbering-Plan Validation | 1 credit per valid number | API docs |
| Phone Intelligence (carrier and line status) | 1 credit per check (invalid numbers outside the US and Canada are free) | Product page |
Questions about area code 303
Where is area code 303?
NANPA assigns area code 303 to Colorado, United States.
In which state does area code 303 sit?
Colorado. 303 is one of 6 area codes the NANPA table assigns to the state.
Which places does area code 303 cover?
The places with the most ZIP codes among the rate centers in 303 are Denver, CO, Longmont, CO and Bennett, CO. The rate center list on this page shows all of them.
Who owns area code 303?
NANPA assigns area codes. Within 303, Qwest holds the most prefixes, 448 prefixes or 57%.
Which time zone does 303 use?
The NANPA NPA report lists the time zone for 303 as Mountain (M).
What year did 303 enter service?
The NANPA NPA report gives an in-service date of 1947-01-01, so 303 has been in use since 1947.
Does area code 303 have an overlay?
Yes. 720 (in service 1998-06-01) and 983 (in service 2022-06-17) share the same area with 303, so numbers from all of them are local to each other.
Which area codes are nearest to 303?
The area codes closest to 303, measured between the centers of the ZIP code places they serve, are 970 (about 61 miles), 719 (about 111 miles), 307 (about 235 miles), 308 (about 254 miles) and 505 (about 298 miles).
How many prefixes does area code 303 have?
NANPA's report dated 2026-10-17 lists 784 prefixes in service in 303, spread over 13 rate centers and 27 holders.
Are there complaints about 303 numbers?
The FCC data on file has 6,982 complaints for 5,710 numbers in 303. They are unverified consumer reports. A number with no complaints on file is not proven safe.
Area code assignments: North American Numbering Plan Administrator NPA report, file dated 10/17/2026, retrieved 2026-10-17. Source file. New codes are assigned several times a year. Prefixes, rate centers, holders, time zone, in-service date and overlays: NANPA central office code report dated 2026-10-17 and NPA report dated 2026-10-18. Complaints: FCC consumer complaints open data, fetched 2026-10-17. ZIP code places: Postal code places and coordinates: GeoNames (geonames.org), licensed CC BY 4.0.