What County Is My ZIP Code In?
Enter a 5-digit ZIP Code. We look it up in the U.S. Census Bureau's ZIP Code area file and show every county that ZIP Code touches, with the share of its area in each county.
Why some ZIP Codes have more than one county
ZIP Codes are drawn by the U.S. Postal Service to route mail. They follow delivery routes, not county or city lines, so a single ZIP Code can include parts of two, three, or even more counties. When that happens, we list each county and the percentage of the ZIP Code's land area that falls inside it.
A large share doesn't guarantee that your home is in that county, because land area isn't the same as where people live. If your ZIP Code spans more than one county, enter your street address for an exact answer.
Before you fill out a form
If a form asks for your county and your ZIP Code touches more than one, don't just pick the county with the largest share. Check your street address instead: a single address can only be in one county. A few ZIP Codes even cross state lines, which is why each county in the result is listed with its state.
ZIP Codes vs. ZIP Code Tabulation Areas
The Census Bureau publishes ZIP Code Tabulation Areas (ZCTAs), which are its best approximation of ZIP Code areas. Most ZIP Codes have a matching ZCTA. Some don't: ZIP Codes used only for P.O. Boxes, for a single large business or university, or for military mail have no area of their own. If your ZIP Code isn't found, that is the most likely reason.
Where the data comes from
County shares come from the Census Bureau's 2020 ZCTA-to-county relationship file. ZCTAs are redrawn after each decennial census, so this list stays the same until the 2030 census. County names come from the Census Bureau's current county boundary service. In Census Bureau data, Connecticut's nine planning regions replaced its eight historical counties in 2022, so for Connecticut we use the 2020 ZCTA-to-town file and group each town into its current planning region.