Where Does Our Data Come From?

Every area code page on this site is backed by official, publicly available datasets. This page explains what we use, how we keep it accurate, and what to do if something looks wrong.

Why you can trust this data

  • Official sources only — area code assignments come from NANPA, the authority that manages North American phone numbering.
  • U.S. Census data — demographic statistics (population, income, education, etc.) are drawn from the Census Bureau's American Community Survey 5-year estimates — a widely-used public dataset.
  • Regularly refreshed — data is updated periodically so new area codes, overlays, and splits appear promptly.
  • Open to correction — if you spot an error, let us know and we'll investigate.

What the data covers

Each area code page can include the following information, all derived from the sources listed below:

  • Geographic coverage — states, cities, and counties served
  • Overlay & split relationships — whether an area code shares geography with another
  • Time zone information
  • Demographic snapshot — population, median household income, poverty rate, unemployment, and education levels
  • City-to-area-code lookups

Coverage note: Demographic statistics require both boundary polygon data and Census ACS data. We have boundary polygons for 331 of 376 geographic area codes, but Census ACS demographic data is available for only 194 of 376. Area codes without demographic data show a "Data Unavailable" notice. When a code lacks its own data, we may use county-based fallback data from a neighboring code that shares overlapping counties.

Methodology note: Population and demographic figures are derived from U.S. Census Bureau county-level data, mapped to area codes using ZCTA (ZIP Code Tabulation Area) centroids and NPA boundary polygons. Because area code boundaries do not align precisely with county lines, these figures are approximate and should not be treated as official census counts. The Census Bureau does not publish population data at the area code level.

Known limitation — ZCTA population assignment: When a ZCTA spans multiple counties, our current methodology assigns thefull ZCTA population to each county. This can causepopulation overestimation for area codes that cover overlapping metropolitan regions. We are working on a proportional allocation method to reduce this bias.

Overlay area codes (e.g., 762 overlaying 706) share the same geographic area as their parent code. Demographic data is shown only for the parent (geographic) code to avoid double-counting. The population shown for a geographic code represents the total service area, which may overlap with other area codes in dense regions.

How accurate is geographic coverage?

We source official area code assignments — including overlays and splits — from authoritative numbering-plan data. For geography, we show coverage at the practical level most people care about (states, cities, and counties), but it's not meant to represent precise, street-level boundaries.

Even with high-quality public datasets, real-world changes can take time to appear. If you believe something is inaccurate, please contact us.

Frequently asked questions

Where does area code data come from?
Area code assignments, overlays, and splits are sourced from official NANPA (North American Numbering Plan Administration) public reports — the same authority that manages phone numbering in the US and Canada.
How accurate is the area code information?
We use authoritative public datasets including NANPA reports and U.S. Census Bureau data. While we strive for accuracy, real-world changes (new area codes, boundary adjustments) may take a short time to appear on the site.
How often is area code data updated?
Data is refreshed regularly from official sources. Area code pages are updated periodically so you always see current information without significant delays.
Where do the demographic statistics come from?
Population, income, poverty rate, and other demographic figures come from the U.S. Census Bureau's American Community Survey (ACS) 5-year estimates — a widely trusted public dataset.

Methodology

Transparency is core to our mission. Below we explain exactly how we process, calculate, and present data — including known limitations.

Area Code Boundaries

We use NPA (Numbering Plan Area) boundary polygons from the Colorado Open Data Portal. These polygons define the geographic service area for each area code. Overlay area codes share the same boundary as their parent code.

Known limitation: Boundary polygons are approximations. Some polygons may not perfectly align with actual service boundaries. We currently cover 331 of 376 geographic area codes.

Census Data

Demographic data (population, income, education, poverty) comes from the U.S. Census Bureau's American Community Survey (ACS) 5-year estimates. The 5-year estimates provide the most reliable data for small geographic areas like individual counties.

Source: data.census.gov

ZCTA-to-County Mapping

We map area codes to counties using Census ZCTA (ZIP Code Tabulation Area) data. ZCTAs are statistical areas created by the Census Bureau that approximate ZIP code boundaries. When a ZCTA spans multiple counties, the full population is attributed to each county (an acceptable approximation for our aggregation method).

Population & Density Calculation

Population: County-level population from Census ACS, aggregated to area codes using ZCTA-to-county mappings. For area codes with multiple counties, populations are summed across all mapped counties.

Population density: Total population divided by total land area (square miles) of all mapped counties. Land area comes from the Census Bureau's Gazetteer files.

Known limitation: Population figures are approximations derived from county-level data mapped to area codes via geographic boundaries. The Census Bureau does not publish population data at the area code level. Overlay area codes share their parent's geography — demographic data appears only once per unique geographic area.

Income & Education

Median household income: Population-weighted median from county-level Census ACS data. Counties with more people contribute more to the weighted average.

Education (Bachelor's degree or higher): Same population-weighted aggregation method applied to county-level education attainment data.

Prefix Utilization

Utilization data comes from the NANPA Prefix Utilization Report. Utilization percentage = (assigned prefixes / total available prefixes) × 100. A prefix is an NXX code (the middle 3 digits of a phone number).

We track utilization across 361 US area codes. Codes above 90% utilization are approaching exhaustion and may need relief (new area code assignment).

Source: NANPA reports

Relief Planning Status

Area codes in "relief planning" status are those where NANPA has initiated the process of adding a new area code (via split or overlay). We track relief status from NANPA planning letters and regulatory filings.

Historical Source Hierarchy

When multiple sources provide conflicting historical information, we prioritize:

  1. NANPA official reports and planning letters
  2. FCC regulatory filings and orders
  3. State public utility commission records
  4. Wikipedia (verified against primary sources)

Update Frequency

NANPA data: Updated every 5 days via automated pipeline.Census data: Updated annually when new ACS estimates are released.Enrichment content: Regenerated periodically with data reconciliation to ensure consistency with canonical data sources.

Known Limitations

  • 42 area codes lack county boundary polygons in the Colorado Open Data source
  • Population data is derived from county-level Census data, not area-code-level
  • Overlay area codes share geography with their parent — demographic data appears once per unique area
  • Utilization data reflects NANPA reports, which may lag actual carrier assignments by weeks

Data Discrepancies

If you notice inconsistent numbers between pages, it may be because:

  • Different data vintages (page generated at different times)
  • Different geographic scopes (US-only vs full NANP)
  • Rounding differences in display formatting

We maintain a canonical data source (canonical-stats.json) that all pages reference. When discrepancies are found, our automated reconciliation pipeline corrects them.

Correction Policy

We operate a multi-layer quality assurance system:

  1. Automated reconciliation: Every data update runs through a reconciliation pipeline that corrects known error patterns
  2. Knowledge Graph validation: All enrichment content is validated against our canonical knowledge graph
  3. Consistency audit: Automated checks verify that all data points match across pages
  4. Manual review: Flagged issues are reviewed and corrected

If you find an error, please report it — we prioritize corrections based on user reports.

Full source list

Below is the complete list of public data sources we rely on, organized by category. Individual area code pages may cite additional regulatory filings, planning letters, and news articles — these are listed in the footnotes of each page.

Primary Data Sources

Regulatory & Government Sources

Individual area code pages cite regulatory filings from these agencies to document the history of splits, overlays, and relief planning.

  • FCC — Federal Communications Commission orders, numbering authority delegations, and consumer guides.fcc.gov · docs.fcc.gov
  • State Public Utility/Service Commissions (PUC/PSC) — area code orders, exhaustion announcements, and docket filings from 40+ states including CA (CPUC), TX (PUC), NY (PSC), FL (PSC), IL (ICC), OH (PUCO), PA (PUC), and others.Examples: cpuc.ca.gov · puc.texas.gov · dps.ny.gov
  • NANPA Planning Letters — 60+ individual planning letters (PL-069 through PL-619) documenting area code relief decisions.nanpa.com/npa-relief/planning-letters
  • FTC / Do Not Call — consumer protection and robocall guidance.consumer.ftc.gov · donotcall.gov

Reference & Research Sources

Additional sources used for historical context, geographic data, and cross-referencing.

News & Media

Local and national news articles cited in individual area code pages for historical context and announcements.

  • Miami Herald · LA Times · SF Chronicle · Houston Chronicle
  • Austin American-Statesman · Milwaukee Journal Sentinel
  • NBC Bay Area · CBS News · CNBC · Florida Today
  • EIN Presswire · PR Newswire · Community Impact
  • Plus 30+ local newspapers and NPR stations