You are probably already using the 720 area code without realizing it. 720, 303, and 983 share the same Denver geography, the same dialing rules, and the same Mountain Time clocks. The differences are administrative, not regional.
You're probably already using the 720 area code without realizing it. If you've called any Denver-area number in the last decade, the number on your phone bill was almost certainly a 720, 303, or the newer 983 — three different area codes sharing the exact same geography, the same dialing rules, and the same Mountain Time clocks. The differences between them are administrative, not regional. A 720 number from a coffee shop in LoDo is no different in coverage from a 303 number across the street.
If you're trying to set up a Denver-area business presence, understand a call you received from a 720 number, or figure out why local calls in Colorado now require 10 digits when they didn't 20 years ago, this guide breaks down how the 720 area code actually works — coverage, the overlay system, dialing rules, history, and how to provision a 720 phone number quickly in 2026.
The 720 area code is a North American Numbering Plan area code covering the Denver metropolitan area in Colorado. It was created in 1998 as an overlay of the existing 303 area code rather than as a geographic split — meaning 720 and 303 share the same physical territory. The Denver metro added a third overlay, 983, in 2021. All three operate under Mountain Time and require 10-digit dialing for local calls.
Most US area codes work like Texas or California outside the major cities — one geographic boundary, one area code. The Denver metropolitan area uses an overlay system instead. Three area codes (303, 720, and 983) all serve the same physical region. Every new phone number provisioned in the Denver metro is assigned to whichever code has available inventory, not based on neighborhood or street.
The overlay model has practical consequences:
Most US metros with population over 1 million have adopted some form of overlay system since the late 1990s for the same reason: pure geographic codes ran out of numbers. The 602 area code (Phoenix) is a notable exception — it still uses geographic splits rather than overlays.
The 720 area code covers the entire Denver metropolitan statistical area across multiple counties. Major cities and neighborhoods using 720 numbers include:
The same boundary is shared with 303 and 983, so any city or neighborhood that has a 303 number also has 720 and 983 numbers in active use.
The entire 720 area code operates in Mountain Time, switching between Mountain Standard Time (UTC-7) in winter and Mountain Daylight Time (UTC-6) under daylight saving. Because of the 303/720/983 overlay, the Denver metro requires 10-digit local dialing — you cannot call a neighbor with seven digits even within the same neighborhood. Domestic callers from outside the metro dial 1 + 720 + 7-digit local number. International callers dial their country's international prefix + 1 (US country code) + 720 + 7-digit local number. The North American Numbering Plan Administration (NANPA) manages all area code assignments and 10-digit dialing mandates across the US and Canada.
The Denver metro area is one of the fastest-growing US economies, anchored by technology (Google's Boulder campus, Palantir, SendGrid), aerospace (Lockheed Martin, Ball Aerospace), telecommunications (CenturyLink/Lumen heritage), energy, healthcare, and a sprawling startup ecosystem. The region added population steadily through the 2010s and 2020s, driving the need for that third 983 overlay.
Businesses provision 720 numbers for:
Local Denver DIDs include 720 area code numbers alongside 303 and 983 inventory, typically provisioned in 24–48 hours. Businesses expanding across multiple metros can compare the 325 area code or the 805 area code for regional coverage options.
The 303 area code was Denver's original code from 1947 — older Denver residents still treat 303 as "the real Denver number." The 720 code was added in 1998 to handle exhausted 303 inventory. Functionally there is no difference between them today. Both serve identical geography, identical dialing rules, identical time zone. Some Denver natives still prefer 303 for emotional reasons, but call-recipient behavior data shows answer rates are statistically equivalent across all three Denver codes.
Provisioning a 720 number through a modern DID provider takes three steps:
The process typically completes in 24–48 hours from order to first inbound call. Numbers stay portable under FCC portability — you can later port your 720 number to a different provider if you switch carriers.
The 720 area code is a textbook case of how modern US metros handle phone-number demand: stack overlays on top of existing geography, force 10-digit dialing for everyone, and stop pretending that area codes correlate with neighborhood. For businesses, the practical implication is freeing — you don't have to chase a scarce 303 number to look "real" in Denver. A 720 line (or a 983 line) reaches the same customers, in the same neighborhoods, with the same answer rates.
Get a 720 area code phone number — local Denver DIDs across 303, 720, and 983 inventory, business and toll-free pairing, and routing to your softphone or PBX within 24–48 hours. No minimum commits, no setup fees. Businesses also provisioning voice termination alongside their local DIDs can review wholesale VoIP providers and wholesale voice services for carrier-layer context.
The 720 area code covers the Denver metropolitan area in Colorado, including Denver, Aurora, Lakewood, Thornton, Westminster, Arvada, Centennial, Boulder, Englewood, Littleton, and surrounding suburbs. The region operates in Mountain Time. The 720 area code was added in 1998 as an overlay of the original 303 code, meaning both codes (plus the newer 983 added in 2021) share the same geographic territory and serve the same cities and neighborhoods.
The 720 area code and 303 area code share the exact same geographic territory in the Denver metropolitan area. Both serve identical cities, neighborhoods, time zone, and dialing rules. The 303 code is older (assigned in 1947) and was Denver's original area code; 720 was added as an overlay in 1998 to handle exhausted 303 inventory. Functionally they are interchangeable — call-answer rates and local recognition are statistically equivalent.
Denver-area numbers require 10-digit dialing because the metro operates under an overlay system with three area codes (303, 720, and 983) sharing the same geography. Without a unique area code per neighborhood, the phone network needs the full area code on every call to route correctly. The mandate started when 720 was added in 1998 and was reinforced when 983 was added in 2021. Most US metros with population over 1 million now require 10-digit local dialing.
The 720 area code was created on October 24, 1998, as an overlay of the existing 303 area code in the Denver metropolitan area. The overlay model was chosen over a geographic split to handle exhausted 303 inventory without forcing existing 303 subscribers to change their numbers. A third overlay code, 983, was added to the same Denver metro region in 2021 to handle continued growth. All three codes operate concurrently with shared geography.
Getting a 303 area code number today is harder than getting a 720 or 983 — most carriers have very limited 303 inventory because the code has been in use since 1947. Some DID providers maintain small 303 inventories from ported-back numbers, but most new Denver-metro provisioning lands on 720 or 983. For business purposes, the three codes are functionally identical in geography, call routing, and answer rates, so 720 typically substitutes well for any 303 use case.
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