The 720 area code is an overlay serving the Denver metropolitan area and Boulder. Introduced in 1998, it was the first overlay layered on top of the established 303 area code to meet booming demand for phone numbers along Colorado’s Front Range.
Quick Summary of the 720 Area Code
| Area Code | 720 |
| State | Colorado (CO) |
| Region | Denver Metropolitan Area & Boulder |
| Major Cities | Denver, Aurora, Lakewood, Boulder, Arvada, Westminster, Thornton, Centennial |
| Time Zone | Mountain Time (MT) – MST / MDT |
| Dialing Format | 10-digit dialing required |
Geographic Coverage
The 720 area code shares an identical footprint with 303, covering the city of Denver and its suburbs of Aurora, Centennial, Lakewood, Arvada, Westminster, and Thornton, along with Boulder to the northwest. Because it is an overlay rather than a separate region, a 720 number and a 303 number can exist on the same street.
Time Zone
The 720 area code observes Mountain Time (MT). Clocks follow Mountain Standard Time (UTC−7) in winter and shift to Mountain Daylight Time (UTC−6) from mid-March through early November. All of Colorado is on Mountain Time. From the West Coast, this region is one hour ahead of Pacific Time, so a 9:00 AM call in California reaches a 720 number at 10:00 AM local time.
Tip: Business hours across the 720 region generally run 9:00 AM to 5:00 PM Mountain Time, Monday through Friday.
How to Dial a 720 Number
Because area code 720 operates as part of an overlay, 10-digit dialing is mandatory for every local and long-distance call. You must dial the full 10-digit number (720 + the seven-digit line number) even when calling a neighbor across the street. For international callers, dial your country’s exit code, then +1 (the North American country code), then 720, followed by the seven-digit local number.
Scam Alerts for the 720 Area Code
Like every U.S. area code, 720 has been used by scammers who spoof local numbers to appear trustworthy. Residents in Denver, Aurora, Lakewood, Boulder, Arvada, Westminster, Thornton, Centennial should stay alert to the following common tactics:
| Scam Type | What to Watch For |
|---|---|
| IRS / Tax Scams | Threatening calls demanding immediate tax payment via gift cards or wire transfer. |
| Utility Shut-off | Impostors claiming to be Xcel Energy threatening to cut power. |
| Tech Support Fraud | Pop-ups or calls claiming your computer is infected and asking for remote access. |
| Prize / Lottery Scam | Calls saying you won a prize but must pay a “fee” or “tax” to claim it. |
If you receive a suspicious call from a 720 number, take these steps to protect yourself:
- Do not share personal information such as Social Security numbers, bank details, or passwords over the phone.
- Hang up and verify by calling the organization back using an official number from its website.
- Report the call to the FTC at reportfraud.ftc.gov and to the Colorado Attorney General’s Office.
- Block the number and consider registering with the National Do Not Call Registry.
Red Flag: Legitimate agencies such as the IRS, Social Security Administration, or your local utility company (Xcel Energy or Colorado Springs Utilities) will never demand immediate payment by gift card, wire transfer, or cryptocurrency. Any 720 caller making such a demand is a scammer.
History and Economy of the 720 Region
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The 720 area code entered service in 1998 as the first overlay for the 303 region, added when the Denver metro began running short of available numbers. A second overlay, 983, joined the same territory in 2023. Overlays let regulators add a fresh supply of numbers without forcing existing customers to change their established phone numbers, so 720 covers precisely the same cities as 303. The regional economy is anchored by aerospace, technology, energy, telecommunications, and finance in Denver, plus the federal research labs, the University of Colorado, and the startup community in Boulder. Many mobile phones and business lines activated since the late 1990s carry the 720 prefix.
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Looking Up a 720 Number
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To identify a 720 caller, use a reverse phone lookup or search the complete 10-digit number online. Because 720 is widely used for mobile numbers, a public search may reveal less about the caller, so never share personal or financial details with an unverified 720 number. If a caller pressures you to act immediately or demands payment, treat it as a likely scam and hang up.
Nearby & Related Area Codes
Colorado is served by several area codes. If you are researching 720, these neighboring and overlay codes are worth knowing:
- 303 – Denver metro (overlay partner)
- 983 – Denver metro overlay (same region)
- 719 – Southern CO / Colorado Springs
- 970 – Northern & Western CO / Fort Collins
You can also browse our full directory of Colorado area codes for more regional guides.
↑ See the complete list of All US Area Codes by State – every area code across all 50 states in one directory.
Explore Neighboring States
Researching area codes just across the state line? Start with these codes in the states that border Colorado:
- Wyoming – area code 307
- Nebraska – area code 402
- Kansas – area code 316
- Oklahoma – area code 405
- New Mexico – area code 505
- Utah – area code 801
- Arizona – area code 602
Frequently Asked Questions
Where is the 720 area code located?
The 720 area code serves the Denver metropolitan area and Boulder as an overlay of 303, covering Aurora, Lakewood, Arvada, Westminster, Thornton, and Centennial.
Why does 720 cover the same area as 303?
720 is an overlay added in 1998 because the 303 region ran short of available phone numbers. Both codes – along with 983 – serve the exact same region.
Do I have to dial 10 digits for 720?
Yes. Overlay area codes like 720 always require 10-digit dialing for local calls.
What time zone is the 720 area code in?
The 720 area code observes Mountain Time (MST/MDT), like all of Colorado.
Related 720 Guides
- Is a 720 call safe? Read Is area code 720 a scam? Spam & safety guide.
- Local coverage: see the Denver area code guide.
- Worried about spam or robocalls? Browse our Scam Alerts directory.