The 303 area code is the original area code of Denver, Colorado. It dates from 1947 and today covers Denver, Boulder and their suburbs together with 720 and 983.
This guide explains where 303 is used, the time zone, how the code shrank from the whole state to the Denver area, and how to handle unknown 303 calls.
303 Area Code Quick Facts
| State | Colorado |
| Location | Denver, Boulder and the surrounding metro area |
| Time zone | Mountain Time (UTC-7, UTC-6 during daylight saving time) |
| In service since | 1947 |
| Type | Original geographic area code |
| Shares its area with | 720 and 983 |
| Toll-free? | No, it is a regular geographic area code |
Check any other code with our free area code lookup tool.
Where Is the 303 Area Code Located?
Area code 303 is located in north-central Colorado, along the Front Range. Main cities:
- Denver
- Aurora
- Boulder
- Lakewood
- Littleton
- Longmont
- Broomfield
- Castle Rock
What Time Zone Is the 303 Area Code In?
Denver is on Mountain Time.
- Mountain Standard Time (MST), UTC-7, in winter
- Mountain Daylight Time (MDT), UTC-6, from mid March to early November
That puts it two hours behind New York and one hour ahead of Los Angeles. Most offices there answer between 9 a.m. and 5 p.m. local time.
History of the 303 Area Code
- 1947: 303 is created for the entire state of Colorado. It stays the only code in the state for 40 years.
- March 5, 1988: southeastern Colorado, including Colorado Springs and Pueblo, becomes 719.
- April 2, 1995: northern and western Colorado become 970. 303 is left with the Denver and Boulder area.
- September 1, 1998: 720 is added as an overlay, and ten-digit dialing becomes required.
- June 17, 2022: 983 is activated as a third code.
Why 303 Is the Number People Want
In Denver, a 303 number is seen as a mark of a long-time local. People who grew up in the city and businesses that have been around for decades usually have one. New 303 numbers are scarce, so most new lines today get 720 or 983. All three codes cover exactly the same area. Our 720 area code guide explains the overlay in more detail.
How to Dial a 303 Number
Dial all ten digits for every call in this area.
- From the US or Canada: 1 + 303 + the seven-digit number
- From another country: your exit code + 1 + 303 + the seven-digit number
Is a Call From 303 a Scam?
A 303 call usually comes from a Denver-area resident or an established local business. Scammers spoof 303 numbers for the same reason locals like them: the code looks trustworthy.
Watch for these warning signs:
- Someone who says they are from the IRS, Social Security or a court and demands payment
- Tech support calls about a virus on your computer
- Investment or crypto offers from a company you do not know
- Texts that ask you to click a link to fix a billing problem
Caller ID can be spoofed, so the number on your screen does not prove where a call comes from.
What to do with an unknown 303 call
- Let it ring out and check the voicemail.
- Search the full number online before you call back.
- Block the number and report it.
- Report scam calls at reportfraud.ftc.gov and register at donotcall.gov.
- Forward spam texts to 7726 (SPAM).
How to Get a 303 Phone Number
A 303 number is easy to get, for personal or business use.
- Carriers: you can ask for a Denver number, but 303 is rarely available. Expect 720 or 983.
- VoIP and virtual number providers: search by area code, pick a 303 number and forward calls to any phone.
- Toll-free numbers: a better fit if your customers are spread across the country.
Read our guides to virtual phone numbers and the 833 area code.
Area Codes Near 303
| 720, 983 | Same area as 303 |
| 719 | Colorado Springs, Pueblo |
| 970 | Fort Collins, Greeley, Grand Junction |
| 307 | Wyoming |
| 505 | Albuquerque and Santa Fe, New Mexico |
Related guides: 720 area code for Denver, 702 area code for Las Vegas, 602 area code for Phoenix.
303 Area Code FAQs
What city is area code 303?
Denver, Colorado. It also covers Boulder, Aurora, Lakewood, Littleton and Longmont.
What is the difference between 303 and 720?
They cover the same area. 303 dates from 1947 and 720 was added in 1998.
Is Colorado Springs in 303?
No. Colorado Springs has used 719 since 1988.
What time zone is 303?
Mountain Time.
Is 303 a toll-free number?
No. Toll-free codes are 800, 833, 844, 855, 866, 877 and 888.
Final Word
The 303 area code has served Denver since 1947 and shares its area with 720 and 983. It is on Mountain Time. Let unknown callers leave a message before you respond.
