Area codes · +1
Area code 303
Area code 303 covers Denver, Colorado. We hold 3,065 allocated blocks for it across 13 rate centres, split 32% mobile, 60% landline and 8% VoIP.
The other area codes laid over 303
Area code 303 does not have Denver to itself. 2 other codes — 720, 983 — serve the same rate centres, laid over the same ground rather than dividing it. That is an overlay: a new code added when the old one ran out of numbers, covering the same streets. Two neighbours can hold different area codes, so the code says roughly when a number was issued rather than where it sits.
Each holds its own blocks and its own carrier mix, so a 303 number and a 720 number from the same street can report different line types. Filtering Denver by area code needs all 3 of them.
303 is not confined to Denver itself: its blocks sit across 13 rate centres, named in the table below.
Colorado is split across 5 area codes — 720, 970, 719, 303, 983. By allocated blocks 303 is the 4th largest of them, holding 14% of the Colorado total.
Where 303 numbers are concentrated
Rate-centre names are reproduced as NANPA records them. The agency truncates them to ten characters, so longer names appear shortened elsewhere on this site.
| Rate centre | Blocks | Share of 303 |
|---|---|---|
| Denver | 2,695 | 88% |
| Fortlupton | 101 | 3% |
| Longmont | 98 | 3% |
| Deckers | 45 | 1% |
| Keenesburg | 33 | 1% |
| Allnspklyn | 22 | 1% |
| Georgetown | 22 | 1% |
| Hudson | 22 | 1% |
| Strasburg | 11 | 0% |
| Deer Trail | 5 | 0% |
| Bennett | 1 | 0% |
| Byers | 1 | 0% |
| Roggen | 1 | 0% |
Carriers holding the most 303 blocks
Qwest Corporation855 blocks
Verizon Wireless323 blocks
T-Mobile Usa, Inc.279 blocks
Onvoy215 blocks
Level 3 Communications, Llc205 blocks
AT&T Wireless188 blocks
The largest holder, Qwest Corporation, has 28% of the code.
These are original allocations. A number keeps its digits and its block when its subscriber moves network, so a ported 303 number still reports the carrier it started with. Closing that gap needs a live query against the routing database. How line type is derived.
Check a single 303 number, or run a whole list through the free cleaner — neither uploads anything.
Common questions
Where is area code 303?
Area code 303 covers Denver, Colorado. It is not the only code there: 720, 983 are overlays on the same rate centres, so a Denver, Colorado number can start with any of them.
Is a 303 number a mobile or a landline?
It can be either, and the digits do not say which. North American mobile and landline numbers share the same ranges, so the answer comes from the carrier holding the block. In 303 the split runs 32% mobile, 60% landline and 8% VoIP, so landline is the most likely single answer.
Which carriers hold 303 numbers?
The largest holders are Qwest Corporation, Verizon Wireless, T-Mobile Usa, Inc.. That is the carrier the block was allocated to, which is not necessarily the network a given number sits on today.
How many 303 numbers are there?
The code holds 3,065 allocated blocks in our copy of the numbering plan. A block is 1,000 or 10,000 consecutive numbers depending on how deeply it has been pooled, so 303 covers on the order of 3,065,000 possible numbers — most of which have never been issued to anyone.