The 720 area code is in Colorado. It covers Denver, Boulder and the suburbs around them. It shares exactly the same area as the older 303 area code and the newer 983 area code.
If a 720 number is calling you, this guide shows where it is registered, what time it is in Denver, and how to tell whether the call deserves a callback.
720 Area Code Quick Facts
| State | Colorado |
| Location | Denver and Boulder metropolitan area |
| Time zone | Mountain Time (UTC-7, UTC-6 during daylight saving time) |
| In service since | September 1, 1998 |
| Type | Overlay area code on 303 |
| Shares its area with | 303 and 983 |
| Toll-free? | No, it is a regular geographic area code |
Look up any other code with our free area code lookup tool.
Where Is the 720 Area Code Located?
Area code 720 is located in north-central Colorado, along the Front Range of the Rocky Mountains. Main cities include:
- Denver
- Aurora
- Boulder
- Lakewood
- Littleton
- Longmont
- Broomfield
- Castle Rock
The rest of Colorado uses other codes. Colorado Springs and Pueblo are in 719. Fort Collins, Grand Junction, Vail and Aspen are in 970.
What Time Zone Is the 720 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 Denver two hours behind New York, one hour behind Chicago and one hour ahead of Los Angeles. If you are on the East Coast, do not call a 720 number before 11 a.m. your time unless you want to wake someone up.
History of the 720 Area Code
For 40 years Colorado needed only one area code.
- 1947: 303 is created for the entire state of Colorado.
- March 5, 1988: 719 is split off for the southeast, including Colorado Springs and Pueblo.
- April 2, 1995: 970 is split off for northern and western Colorado. 303 is left with the Denver and Boulder area.
- September 1, 1998: 720 is added as an overlay on 303. Ten-digit dialing becomes required for local calls.
- June 17, 2022: 983 is activated as a third code for the same area.
By the late 1990s the Denver area was growing so fast that 303 could not supply enough numbers for new mobile phones, pagers and second lines. An overlay let everyone keep their 303 number while new customers received 720.
303 vs 720: Is There a Difference?
Not in coverage or cost. Both codes serve the same cities, and a call between them is local. The only difference is perception. Long-time residents tend to have 303 numbers, so 303 is sometimes seen as the “old Denver” code. Newer residents and newer businesses usually have 720 or 983.
How to Dial a 720 Number
- From the US or Canada: 1 + 720 + the seven-digit number
- From abroad: your exit code + 1 + 720 + the seven-digit number
Inside the Denver area you still need all ten digits, because three area codes share the same territory.
Is a Call From 720 a Scam?
The 720 area code is legitimate and widely used by hospitals, universities, tech companies and government offices in the Denver area. Scam callers use it as well, often with a spoofed number.
Common tricks to watch for:
- Calls about an arrest warrant or missed jury duty that can be “fixed” with a payment
- Utility shut-off threats that demand payment within the hour
- Fake bank or card fraud alerts asking for your PIN or a passcode
- Texts about unpaid tolls with a link to pay
Real courts, utilities and banks do not ask for gift cards, crypto or payment apps over the phone.
What to do with an unknown 720 call
- Let it ring out. A real caller will leave a message.
- Do not confirm personal details to someone who called you.
- Call the organization back on the number from its website or your bill.
- Block the number and turn on your carrier’s spam filter.
- Report scam calls at reportfraud.ftc.gov and register at donotcall.gov.
- Forward spam texts to 7726 (SPAM).
How to Get a 720 Phone Number
- Mobile carriers: new lines in the Denver area are assigned 720 or 983 numbers, depending on what is free. New 303 numbers are scarce.
- VoIP and virtual numbers: choose a 720 number online and forward it to your current phone. This suits remote businesses that want a Denver presence.
- Toll-free option: if your customers are spread across the country, a toll-free number may work better than a local one.
Read more in our guides to virtual phone numbers and the 833 area code.
Area Codes Near 720
| 303, 983 | Same area as 720: Denver, Boulder, Aurora |
| 719 | Colorado Springs, Pueblo and southeastern Colorado |
| 970 | Fort Collins, Greeley, Grand Junction and western Colorado |
| 307 | Wyoming |
| 505 | Albuquerque and Santa Fe, New Mexico |
720 Area Code FAQs
What city is area code 720?
Denver, Colorado. The code also covers Boulder, Aurora, Lakewood, Littleton, Longmont and other nearby cities.
Is 720 a cell phone area code?
It is used for both mobile and landline numbers. Many 720 numbers are mobile because the code arrived in 1998, during the cell phone boom.
Is 720 a toll-free number?
No. Toll-free codes are 800, 833, 844, 855, 866, 877 and 888.
What state is area code 720 in?
Colorado.
Why do I keep getting calls from 720 numbers?
Telemarketers often use numbers from large metro areas. If you have no ties to Colorado, let unknown 720 calls go to voicemail and block the ones that leave no message.
Final Word
The 720 area code covers Denver and Boulder on Mountain Time and has been in service since 1998. Treat a call you expect as normal, and screen the rest.
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