Frequently asked questions
What is the difference between a ZIP code and a ZCTA?
A USPS ZIP code is a set of mail delivery routes — essentially lines along streets, not an area. A ZIP Code Tabulation Area (ZCTA) is the Census Bureau's polygon approximation of it, built by assigning census blocks to whichever ZIP is most common inside them. There are about 41,700 ZIP codes and about 33,600 ZCTAs. Demographic data exists only for ZCTAs.
Why do some ZIP codes have no population?
Because nobody lives there. USPS assigns some codes exclusively to PO Box clusters, and others to a single high-volume recipient — a government office, a university mailroom, a large business. These have no residential census blocks, so no ZCTA, so no demographics. We label these clearly rather than printing a population of zero.
How accurate are the population figures?
They are survey estimates from the American Community Survey, not a count. Each carries a margin of error at 90% confidence, which we display. For small ZIP codes the margin can be large relative to the estimate — treat the direction as more reliable than the exact figure.
How often is the data updated?
ACS 5-Year Estimates are released each December. Gazetteer files update annually. Weather is live on every page load.
Can I use this data commercially?
The underlying Census data is US public domain — free to use. GeoNames is CC BY 4.0 and requires attribution. OpenStreetMap is ODbL. Our presentation is ours.
Why does the median income differ from other sites?
Most likely a vintage mismatch. Ours is the 2019–2023 5-Year Estimate for the ZCTA. Some sites use 1-Year estimates (unavailable for most ZIPs), older vintages, or proprietary models. We state ours on every page.