Methodology & Data Sources

The list of area codes, their status, and overlay relationships come from NANPA (the North American Numbering Plan Administrator) – specifically the NPA database and the Central Office (CO) Code assignment records. Two codes are treated as an overlay pair when NANPA assigns them to the same geographic area, which is why overlaid regions require ten-digit dialing.

Population figures come from the U.S. Census Bureau Population Estimates Program, Vintage 2024 (table SUB-IP-EST2024-POP for incorporated places). We use the most recent official vintage rather than older decennial counts, so the numbers reflect current population as closely as public data allows.

This is the part most directories gloss over. Area codes are assigned to rate centers – telephone-routing zones – not to city limits. A single area code usually spans many rate centers, and a large metro can be split across several codes. So when we show a “primary city” for a code, it means the largest place in that code's service area, not that the code belongs only to that city.

One consequence matters for callers: an area code shows where a number was assigned, not where the caller physically is. Numbers move with people, port to VoIP, and are routinely spoofed. An area code is a strong hint about origin, never a proof of location.

The per-code prefix (NXX) tables and the carrier for each prefix are built from NANPA CO Code assignment records. We label a prefix as wireless, landline, or unknown by matching the operating company name against a maintained list of wireless carrier patterns; where a name is ambiguous, we leave it as unknown rather than guess.

The “reports” figures come from the FTC Do Not Call Reported Calls data. We aggregate complaints strictly at the area-code level of the calling number over a rolling recent window, and show the count, the share flagged as robocalls, and the most common complaint subjects.

Two caveats travel with these numbers. Caller ID is easy to spoof, so a complaint about a number showing a given code does not mean the caller was in that area. And the FTC does not verify the details of individual complaints. We never label a specific number or person a scammer; the data describes an area code, not an individual.

For NANP codes outside the US (Canada and Caribbean territories) we use the national numbering authorities alongside NANPA records. Special-use codes – toll-free, N11 service codes, premium and non-geographic ranges – are described from NANPA's assignment records and FCC rules governing how each range may be used and billed.

The underlying dataset was last refreshed in June 2026. We re-pull the official sources on a regular schedule so the figures stay current, and each area-code page shows the source and date for its data. If you spot something wrong, please tell us through the contact form.