--- title: "Area code 303: Colorado, United States" url: "https://lookvalid.com/area-code/303.md" canonical_url: "https://lookvalid.com/area-code/303" last_updated: "2026-10-23" type: "reference" summary: "Area code 303 serves Colorado, United States. Number formats, numbering rules, a live phone validator and the other codes in Colorado." --- # Area code 303: Colorado, United States Area code 303 serves Colorado, United States. Number formats, numbering rules, a live phone validator and the other codes in Colorado. NANPA lists 784 central office codes (prefixes) in use in area code 303, held by 27 holders across 13 rate centers. The largest rate center is DENVER, with 735 prefixes (94%). Qwest holds the most prefixes, 448 (57%). 29% of the prefixes are pooled, which means their thousands-blocks can belong to different companies. The FCC unwanted-call data has 6,982 complaints on file for 5,710 numbers in 303, most often filed as "Unwanted Calls". These are consumer reports, not findings. ## Facts - 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 | 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% | ## Carriers | 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. ## History - 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. ## Nearest area codes 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). ## ZIP codes 79 ZIP codes fall in places that have a rate center in this area code. The places with the most are Denver, CO (66 ZIP codes), Longmont, CO (4 ZIP codes) and Bennett, CO (1 ZIP code). A ZIP code and an area code are unrelated systems, so a ZIP code can sit in more than one area code and an area code spans many ZIP codes. ## Complaints on file 6,982 complaints for 5,710 numbers. Numbers whose latest complaint falls in each year: - 2023: 197 - 2024: 134 - 2025: 195 ## Questions ### 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. Sources: NANPA central office code report dated 2026-10-17; NANPA NPA report dated 2026-10-18; FCC unwanted-call complaints, data fetched 2026-10-17; ZIP code places from GeoNames (CC BY 4.0).