Data sources and methods

The database covers 41,705 zip codes. 33,791 of them have a residential delivery area that the Census Bureau maps as a ZIP Code Tabulation Area (ZCTA), and those get full demographic profiles. The rest are PO box, single-organization and military codes, which have no resident population of their own.

Sources

Postal codes: GeoNames postal code database (CC BY 4.0)
The list of every zip code, including PO box, single-organization and military codes, with the USPS preferred city name and an approximate location.
Demographics: U.S. Census Bureau, American Community Survey 5-year estimates
Population, age, race and ethnicity, income, poverty, housing, education, commuting, language, internet access, veterans, nativity, health insurance, and the occupations, industries, employers and earnings of working residents. Published for ZIP Code Tabulation Areas, counties, states and the nation.
Boundaries: Census Bureau ZIP Code Tabulation Areas (2020), cartographic boundary file
The polygons drawn on each zip page, simplified for fast maps.
Area and center points: Census Bureau Gazetteer files
Land and water area plus an interior point for each ZCTA and county.
Counties and places: Census Bureau 2020 ZCTA relationship files
Which counties and cities each zip overlaps, weighted by land area.
Time zones: IANA time zone boundaries (via geo-tz)
The time zone at each zip's center point.

Methods

Estimates and vintage. Demographic figures are 2020–2024 American Community Survey 5-year estimates, the most recent release available for zip-level areas. They are survey estimates, so small zip codes can have large margins of error.

Zip codes vs. ZCTAs. The Postal Service defines zip codes as delivery routes, not areas. The Census Bureau builds ZCTAs by grouping census blocks by their most common zip code. ZCTAs match postal zip codes closely but not exactly.

Capped values. The Census Bureau caps reported medians at both ends: household income at $250,000+ and under $2,500, home value at $2,000,000+ and under $10,000, rent at $3,500+ and under $100, year built at “1939 or earlier” and rooms at “9 or more”. We show those as ranges and leave them out of ratios like home value to income.

Small and empty areas. Some zip areas have very few or no residents (airports, bases, parks, business districts). Estimates for zips under 500 residents carry a warning, and zips with no residents show no demographic profile.

Island areas. The American Community Survey doesn't cover Guam, the U.S. Virgin Islands, American Samoa or the Northern Mariana Islands, so their zip pages list location details only.

Percentiles and ranks. A zip's national percentile is the share of Americans who live in a zip code with a lower value, so the 50th percentile is what a typical American experiences. (Counting every zip equally would let thousands of tiny rural zips push almost any city zip into the 90s.) State ranks simply order a state's zip codes from highest to lowest. Both include zip codes with at least 100 residents. Rankings pages include zip codes with at least 1,000 residents, so a single prison or campus doesn't top a list.

Similar zip codes. Each zip with 1,000+ residents is compared with every other zip on ten standardized measures: median income, home value, age, density, education, homeownership, work from home, poverty, share over 65 and median year built. The closest matches more than about 100 miles away are listed.

Diversity index. The chance that two randomly chosen residents belong to different race or ethnicity groups, from 0 (everyone the same) to 100.