All about ZIP Codes: ZCTA Supplement

Revised 2025

ZCTA Master Data Set

The MCDC's zcta_master_2023 dataset combines geographic and demographic data regarding ZCTAs and contains demographic indicators taken from the most recently available American Community Survey data. The dataset also contains congressional district codes, updated PUMA codes, CBSAs (metropolitan and micropolitan statistical areas), metropolitan divisions, and combined statistical areas (CSAs).

Decennial Census Data

Summary File 1 (DHC in the 2020 census) contains data tables summarizing the results of the decennial census survey. Data for ZCTAs appear with summary level codes of 871 (ZCTA within state) on the individual state files. The national files have summaries for all ZCTAs in the nation and has three summary levels: 860 (complete ZCTAs), 870 (ZCTAs within state — same data as the 871 summaries on the state files but with a different summary level code), and 880 (ZCTAs within county). Since over 90% of all ZCTAs are contained within a single county, you mostly get three copies of the same tabular data on the national file. These data can be accessed via the data.census.gov application at the Census Bureau, or they can be accessed from MCDC's public data archive using the Uexplore/Dexter query tools.

American Community Survey Data

If you are not familiar with the ACS, we recommend you see our American Community Survey page for basic background information. Basically, ACS does for 2010 and 2020 data what SF3 did for 2000 data, except that it is not simple one-point-in-time data derived from a census, but rather uses survey data collected over a five-year period. New data are normally released in December each year.

You can access these data from data.census.gov at the Census Bureauor via the MCDC public data archive MCDC's data archive using Uexplore/Dexter.

Geocorr

We now have multiple versions of the Geocorr geographic correspondence engine. The newest version is Geocorr 2022. You can use this to relate the new codes to all the others such as counties, metro areas, urban/rural, PUMAs (both old and new), census tracts, congressional districts, etc.

Geocorr generates correlation lists — files that define the correlation of one type of geography (such as ZCTAs) to another. We have also created a directory of commonly requested equivalencies where the source gecode is ZCTA and the target geographies vary for each file in the directory.

ZIP Codes are not ZCTAs

We sometimes like to think of ZIP codes and ZCTAs as more or less the same thing, the only difference being that ZCTAs are "rounded off" to census blocks while real ZIP codes are not. That is mostly true when talking about standard residential ZIP codes, but there are other ZIP codes that are neither "standard" nor residential — the ZIP code for Reader's Digest, for the North Pole (Santa Claus), for the University of Missouri, for Camp Pendleton, for Google headquarters, etc. These are the special (aka "point", "unique", etc.) ZIP codes that are important to the post office and to the entities that use them to receive their mail. But they are not spatial areas (they are points in most cases) and people do not live in them.

A dataset provides a crosswalk between all (or at least mostly all) current ZIP codes and the ZCTAs to which they correspond. For standard residential ZIP codes, it's simple: They are the same codes. For example, for ZIP code 65211, the ZCTA is 65201. For others, access the zip2zcta10 (for 2010), zip2zcta15 (for 2015), or zip2zcta20 (for 2020) datasets.

HUD and USPS Provide Links Between ZIP Codes and Census Tracts

The HUD-USPS ZIP crosswalk files provide a very useful tool for relating ZIP codes and census tracts. These are actual true ZIP codes (not ZCTAs, and including all the "special" ZIPs, such as point ZIPS and P.O. box ZIPs). These files are available quarterly going back to 2010. You may choose a quarter and a crosswalk type and download an Excel file with data for the entire country (including Puerto Rico). Each record/row of the file specifies a five-digit ZIP code and a census tract (including state and county codes). The degree of intersection between the two geographic entities is measured using a set of four ratio variables. RES_RATIO specifies the portion of all residential deliveries within the ZIP code which are in the tract. (This is on the ZIP-to-tract type file; on the tract-to-ZIP type this variable measures the portion of the deliveries within the tract that are within the ZIP.) BUS_RATIO is the same concept but only works with business addresses. OTH_RATIO handles addresses that are neither residential nor business. Finally, TOT_RATIO measures the portion of all addresses regardless of type. Note that these are all ratios with no actual counts.

The intened use of these crosswalks is for allocating data between the two types of geography. Use the ZIP-to-tract correspondences/ratios to allocate data already available at the ZIP level to census tracts. Use the tract-to-ZIP to allocate data at the tract level to ZIP.