720 Area Code: Location, Cities, Time Zone & Phone Number Guide

The 720 area code is a Colorado telephone area code serving the Denver-Boulder region and surrounding communities in north-central Colorado. It is part of the 303/720/983 overlay complex, so 720 does not represent a separate geographic zone from 303 or 983. All three area codes can be assigned within the same general service area.

If you received a call or text from a 720 phone number, the number is associated with the Denver-area numbering region. However, the area code alone cannot tell you exactly which city the caller is in, which carrier they use, or whether the caller is physically located in Colorado at the time of the call.

Here is what you need to know about the 720 area code, including its location, cities, relationship with 303 and 983, time zone, dialing rules, history, and what a 720 number means today.

Where Is the 720 Area Code Located?

The 720 area code is located in Colorado, primarily serving the greater Denver-Boulder metropolitan region and nearby Front Range communities. Denver is the largest and most prominent city associated with the numbering area, but the code is not limited to Denver itself.

The important point is that 720 is an overlay area code. Instead of dividing Colorado into a separate 720 geographic zone, it shares the same general numbering-plan area as 303 and 983. The North American Numbering Plan Administrator (NANPA) currently identifies Colorado’s 303/720/983 combination as an overlay complex with 10-digit local dialing.

This means two people living in the same neighborhood could have different area codes. One person might have a 303 number, another a 720 number, and another a 983 number.

What State Is Area Code 720 In?

Area code 720 is in Colorado, United States.

It is associated most strongly with the Denver metropolitan area and nearby communities along Colorado’s Front Range. The area code does not indicate that a caller is specifically inside Denver city limits.

Which Cities Use the 720 Area Code?

The 720 area code is used across a broad group of cities and communities in the Denver-Boulder region. Major communities associated with the 303/720/983 overlay include:

• Denver
• Aurora
• Boulder
• Lakewood
• Thornton
• Arvada
• Westminster
• Centennial
• Longmont
• Littleton
• Englewood
• Broomfield
• Castle Rock
• Brighton
• Commerce City
• Highlands Ranch
• Parker
• Northglenn
• Lafayette
• Golden

The exact availability of a particular area code can vary by exchange and numbering assignment, so a city’s association with the overlay does not mean every telephone number in that city begins with 720. Current city listings show multiple area codes across the same communities.

Does 720 Mean the Caller Is in Denver?

No. A 720 phone number does not necessarily mean the caller lives in Denver.

Denver is the primary city associated with the area code, but 720 numbers are also used throughout the broader numbering region. Someone with a 720 number could live or operate a business in another community such as Aurora, Boulder, Lakewood, Thornton, or one of the surrounding areas.

There is another important limitation: mobile and VoIP users can keep numbers after moving, so the area code does not reliably establish a person’s current physical location.

720 Area Code Location at a Glance

Detail	Information
Area code	720
State	Colorado
Primary region	Greater Denver-Boulder area
Major city	Denver
Overlay complex	303 / 720 / 983
Time zone	Mountain Time
Local dialing	10 digits
In service since	1998
Numbering type	Geographic area code

Read More: 720 Area Code

NANPA’s current numbering information confirms that 720 belongs to the 303/720/983 overlay complex and uses a 10-digit local dialing plan.

How Is 720 Connected to 303 and 983?

The relationship between 303, 720, and 983 is one of the most important things to understand about this region.

An overlay occurs when multiple area codes serve the same geographic area. Instead of assigning one code to one side of a city and another code to the other side, an overlay allows new telephone numbers to receive a different area code within the existing service region.

Area code 720 was introduced as an overlay for 303 in 1998. NANPA’s planning records document the 1998 overlay of 303 with 720.

The region later received another overlay code, 983. NANPA assigned 983 to overlay the existing 303/720 area, and the new code entered service on June 17, 2022.

303 vs. 720 vs. 983

Area Code	Role in the Region	In Service
303	Original Denver-area code	1947
720	Overlay for the 303 region	1998
983	Additional overlay for the same region	2022

The three codes are therefore not three separate Denver-area zones. They form one overlay complex. A 720 number and a 303 number can belong to people living next door to each other.

When Did the 720 Area Code Start?

The 720 area code was introduced in 1998 to provide additional numbering capacity for the Denver-area region. Contemporary NANPA planning records document the overlay of 303 with 720 in March 1998, while area-code reference records identify June 1, 1998, as the 720 in-service date.

The need for additional numbering capacity was connected to continued growth and demand for telephone numbers in the Denver region. Rather than splitting the existing territory into a new geographic area, 720 was implemented as an overlay.

That approach allowed existing 303 customers to keep their telephone numbers while new numbers could be assigned from the additional area-code pool.

As of 2026, the 720 area code has been in service for about 28 years.

Why Does Denver Have Three Area Codes?

Denver and its surrounding communities have three area codes because the region needed additional telephone-numbering capacity over time.

The original 303 area code dates to the beginning of the North American Numbering Plan in 1947. As demand for numbers increased, 720 was introduced in 1998. The region later received 983, which became active in 2022.

The important practical difference between an overlay and a traditional area-code split is that an overlay does not assign each code to a different physical section of the region.

Instead, the codes coexist.

That is why a Denver-area address can potentially have a 303, 720, or 983 telephone number.

Do You Have to Dial 10 Digits With a 720 Number?

Yes. Ten-digit dialing is used for local calls within the 303/720/983 overlay region. That means callers use the three-digit area code plus the seven-digit telephone number rather than relying on seven-digit local dialing. NANPA identifies the 303/720/983 complex as a 10-digit dialing area, and Colorado’s regulatory guidance confirms that customers in the overlay region use 10 digits for local calls.

For example, a local number would be dialed in this general format:

720-XXX-XXXX

The same principle applies when calling a number with 303 or 983 from within the overlay region.

Why Is 10-Digit Dialing Required?

With multiple area codes serving the same geographic area, the telephone network cannot determine the intended destination from only the seven-digit local number.

Requiring the area code removes that ambiguity.

NANPA explains that 10-digit dialing is a regulatory requirement associated with overlay area codes and provides dialing parity among the codes serving the same region.

What Time Zone Is the 720 Area Code In?

The 720 area code operates in Mountain Time, the time zone used throughout Colorado. The Denver region observes the seasonal transition between Mountain Standard Time and Mountain Daylight Time.

That means the UTC offset changes during the year:

• Mountain Standard Time (MST): UTC−7
• Mountain Daylight Time (MDT): UTC−6

The area-code region is associated with the America/Denver time zone.

If you are scheduling a call with someone who has a 720 number, use Colorado’s current local time rather than assuming the number is always seven hours behind UTC.

Read More: 720 Area Code

Are Calls Between 303, 720 and 983 Local Calls?

The fact that three area codes share the same overlay does not mean every possible call involving those codes is automatically free under every telephone plan.

Colorado’s regulatory guidance states that the overlay does not by itself change what was previously considered a local call, and customers continue to use 10-digit dialing for local calls within and between the overlay area codes.

Whether a particular call has a charge depends on the customer’s carrier, service plan, and applicable calling arrangements.

For that reason, it is better not to assume that the area code alone determines billing. If you are concerned about long-distance or international charges, check the terms of the specific phone plan.

What Does a 720 Phone Number Tell You?

A 720 phone number can tell you that the number belongs to the Denver-area numbering region in Colorado.

It does not reliably tell you:

• The caller’s exact city
• The caller’s current physical location
• The person’s address
• The person’s telephone carrier
• Whether the number is a mobile, landline, or VoIP number
• Whether the caller is currently in Colorado

Area codes identify numbering regions, not people.

This distinction is especially important for mobile phones and internet-based phone services. A person can retain an established number after moving to another city or state.

Can You Get a 720 Phone Number?

Yes. A 720 number can be assigned when a carrier or phone-service provider has suitable numbering inventory available in the desired service area.

Consumers may encounter 720 numbers through mobile, landline, business, or VoIP services. However, choosing a specific area code is not always guaranteed. Availability depends on the provider, the type of service, and the numbers currently available for assignment.

Businesses may also use a 720 number when they want a telephone identity associated with the Denver metropolitan region.

If you are specifically looking for a 720 number, ask the provider whether the requested area code is available before completing the order.

Is a Call From a 720 Number Safe?

The 720 area code itself does not indicate whether a call is legitimate or fraudulent.

A familiar-looking Colorado area code should not automatically be treated as proof that the caller is trustworthy. Conversely, receiving a call from 720 does not mean the caller is a scammer.

If an unexpected caller asks for passwords, verification codes, financial information, payment, or other sensitive information, verify the caller independently before sharing anything.

The area code is geographic numbering information, not an identity-verification system.

Frequently Asked Questions