How Are Area Codes Assigned? NANPA Explained

Area codes in the US are assigned by NANPA (North American Numbering Plan Administration), a private contractor operating under FCC authority.

When the supply of numbers inside an existing area code nears exhaustion, NANPA triggers a relief process that results in either a geographic split or an overlay — creating a new three-digit code to absorb demand.

The system governs over 20 countries, covers more than 313 geographic codes in the US alone, and has been in continuous operation since 1947.

Who assigns US area codes?

NANPA is the neutral administrator designated by the Federal Communications Commission (FCC) to manage the North American Numbering Plan (NANP).

The current NANPA contractor is Somos, Inc., which won an FCC-procured contract in December 2020 for an eight-year term. Before Somos, the contract was held by Neustar. The FCC re-bids the contract periodically; the administrator must remain neutral and cannot be a carrier that benefits from the assignments it makes.

The authority chain flows like this: FCC → state Public Utility Commissions (PUCs) → NANPA → carriers.

The FCC sets the rules. State PUCs (such as the California PUC, the New York Public Service Commission, or the Texas PUC) review NANPA relief recommendations and authorize the final implementation method for their jurisdictions. NANPA then coordinates the actual code assignment and implementation timeline with carriers.

For official code data, see nationalnanpa.com and the FCC area code information page.

How NANPA picks a new area code number

Each area code (formally called a Numbering Plan Area or NPA) is a three-digit code in the format NXX, where:

• N = any digit 2 through 9 (0 and 1 are excluded — 0 signals operator, 1 signals long-distance)
• X = any digit 0 through 9

That structure allows for up to 800 possible area codes in theory, though a significant share are restricted or reserved.

Within each area code, carrier customers are assigned central office (CO) codes, also called NXX codes, which form the first three digits of a 7-digit local number. There are 792 assignable CO codes per area code, and each CO code covers 10,000 subscriber numbers — giving each area code a theoretical capacity of 7.92 million phone numbers.

NANPA follows strict rules when selecting a new code: it deliberately avoids assigning a code that looks similar to neighboring area codes to reduce misdials. When a second code was overlaid on 508 in eastern Massachusetts, NANPA chose 774 — numerically distant to minimize confusion.

What triggers a new area code?

NANPA monitors CO code assignments across every active area code in real time. Carriers must request CO codes from NANPA before they can assign new local numbers — so NANPA has a near-complete picture of utilization.

When forecasts show a particular area code will exhaust its assignable CO codes within approximately 36 months, NANPA issues a formal notification to the state regulatory commission.

At that point the relief planning process begins: industry stakeholder meetings, analysis of viable relief options, public comment periods, state commission hearings, and final authorization. The 36-month window is the minimum — NANPA aims to start the process with enough runway to avoid an actual number shortage during implementation.

Split vs overlay: how NANPA decides

Two relief methods exist, and the difference matters for every business with a local number in an affected area.

Geographic split: The existing NPA territory is divided into two geographic zones. One zone retains the original area code; the other transitions to a new code. Customers in the new zone must update stationery, websites, and dial strings. Within each new zone, 7-digit local dialing can continue. Splits were the dominant method until the late 1990s.

Overlay: A new area code is assigned to the same geographic area, covering the same cities and counties as the original. Existing customers keep their numbers. New subscribers (or those porting in for the first time) may receive a number under either code. The tradeoff: 10-digit dialing becomes mandatory everywhere in the overlay region, even for local calls.

Overlays became the default method after widespread complaints about splits — particularly from businesses that had printed the old area code on thousands of materials. The New York Public Service Commission, for instance, has consistently chosen overlays over geographic splits for more than two decades.

Recent NY overlay authorizations: 465 for NYC metro (2025), 624 for Western NY (2022), 329 for Hudson Valley (2022), and 363 for Nassau County (2022).

The state PUC role

NANPA cannot unilaterally implement a new area code. Every relief plan must be reviewed and authorized by the state Public Utility Commission (or equivalent body) in the affected jurisdiction.

The process at the state level includes:

1. NANPA submits a formal petition with exhaustion forecast and proposed relief options.
2. The state commission publishes the petition for public comment.
3. Stakeholder hearings may be held — telecom carriers, consumer advocates, business groups, and individual residents can all participate.
4. The commission issues a final order selecting the relief method (split or overlay) and the implementation schedule.
5. NANPA and carriers implement under the commission’s timeline.

State commissions vary in how quickly they act and which method they prefer. California’s CPUC, for example, has authorized several overlays in recent years including the 657 overlay on 714 in Orange County and the 945 overlay on 972/214 in the Dallas-Fort Worth region (authorized by the Texas PUC).

How long does the assignment process take?

From NANPA’s initial 36-month notification to the date a new area code goes live, the typical implementation window is 12 to 24 months.

The timeline breaks down roughly as follows:

• Months 1–3: NANPA issues exhaustion forecast; state commission dockets the proceeding.
• Months 3–9: Public comment period, stakeholder meetings, commission hearings.
• Months 9–12: State commission issues final order with chosen relief method and go-live target.
• Months 12–18: Carriers implement routing changes; permissive dialing window opens (both old and new dialing patterns work).
• Month 18–24: Mandatory cutover — the new dialing requirements fully apply.

The permissive dialing window is the “grace period” for consumers and businesses to update their systems before the new pattern is required.

Why some codes are permanently reserved

Certain three-digit combinations are structurally off-limits as geographic area codes.

N11 service codes are the most important reserved block. Any code in the format X11 — where X is 2 through 9 — is permanently reserved for special services:

Code	Service
211	Community and social services
311	Non-emergency local government
411	Directory assistance
511	Traffic and travel information
611	Carrier repair and customer service
711	Telecommunications Relay Services (TRS)
811	Call before you dig (utility lines)
911	Emergency services

Beyond the N11 block, 555-0100 through 555-0199 are permanently reserved for fictional use in TV, film, and advertising — which is why every fake phone number in a Hollywood movie starts with 555.

The original 1947 NANP design also used the middle digit as a structural signal: codes with 0 as the middle digit (like 202, 303, 404) were assigned to states or provinces that had only one area code. Codes with 1 as the middle digit (like 212, 213, 312) went to states needing multiple codes. That original pattern is now historical — the middle-digit rule was abolished as the NANP ran out of structurally pure codes.

Area code assignment FAQ

Area code assignment FAQ

Who is responsible for assigning US area codes? +

NANPA (North American Numbering Plan Administration) is responsible for assigning area codes in the United States and 19 other NANP countries.

NANPA is a private contractor — currently Somos, Inc. — selected and overseen by the FCC. It works with state Public Utility Commissions to authorize and implement new codes.

How does NANPA decide when a new area code is needed? +

NANPA continuously tracks how many central office (CO) codes have been assigned to carriers within each area code. Each area code holds 792 assignable CO codes.

When projections show the pool will exhaust within roughly 36 months, NANPA notifies the state regulatory commission and begins the relief planning process.

What is the difference between an area code split and an overlay? +

A split divides the existing geographic area into two zones. One zone keeps the original area code; the other gets a new one. Customers in the new zone must update their number's area code.

An overlay assigns a second area code to the same geography. No one has to renumber, but everyone must dial 10 digits for all local calls. Overlays are now the standard approach in most states.

Why are some area codes like 911 and 411 unavailable? +

Codes in the N11 format — where N is any digit 2 through 9 followed by two 1s — are permanently reserved as service codes.

Examples: 911 (emergency), 411 (directory assistance), 311 (non-emergency government), 211 (community services), 811 (call before you dig), and 711 (relay services for the hearing-impaired). These cannot be used as geographic area codes.

How long does it take to roll out a new area code? +

From the point NANPA formally notifies a state commission to the date the new code goes live, the process typically takes 12 to 24 months.

The timeline includes a public comment period, state commission hearings, carrier implementation work, and a permissive dialing window where both old and new codes coexist before mandatory activation.

Does a new area code mean my business phone number changes? +

With an overlay, no — existing numbers keep their area code. Only new numbers assigned after the overlay launches carry the new code.

With a geographic split, businesses in the zone assigned the new code must update their area code. Carriers are required to provide advance notice, and a transition window is given before the old code stops working in that zone.

How many area codes are there in the US? +

There are more than 313 geographic area codes currently assigned in the United States, plus a set of non-geographic codes (toll-free 800, 888, 877, 866, 855, 844, 833, and 822 series) and specialized codes.

NANPA publishes an updated list of all assigned NPAs (Numbering Plan Areas) at nationalnanpa.com.

Can I choose a specific area code for my business number? +

Yes. VoIP providers including DialPhone let you select any available area code when you provision a business number — regardless of where your business is physically located.

This means a startup in Austin can present a 212 (New York) or 415 (San Francisco) number to establish a local presence in those markets. Availability depends on the current CO code inventory for that area code.

Get a business phone number with any area code

DialPhone monitors NANPA exhaustion forecasts across all 313+ geographic area codes, so our customers always have visibility into which markets are approaching overlay transitions.

When you provision a business line through DialPhone, you choose your area code — whether that’s a 212 (New York), 213 (Los Angeles), or 415 (San Francisco) number — regardless of where your team is located.

Explore available numbers by state: California area codes · New York area codes.

Browse all codes at our area codes hub, check DialPhone pricing, or start a free trial to claim your number today.

For more on how business phone numbers work, see the DialPhone business phone overview, our number porting guide, and the STIR/SHAKEN explainer for how caller ID authentication works with NANP numbers.