# ZIP Code County Lookup

> ZIP code county lookup: find the county, state, and FIPS code for any US ZIP code instantly, for tax rates and address checks. Free, no signup, runs locally.

- **Canonical URL:** https://boringtoolskit.com/zip-county-lookup-calculator/
- **Category:** Converters
- **Evidence level:** authored-methodology
- **Reviewed:** July 26, 2026
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

This tool is a lookup, not an arithmetic calculation. It takes your five digit ZIP code and matches it against a reference table that stores the county or county equivalent, the county FIPS code, latitude, longitude, time zone, and population for each ZIP. The matching row is returned directly, so the result is one exact record rather than a computed number.

## Worked example

Type 00601 into the lookup and it matches the reference row for Adjuntas: county Adjuntas, Puerto Rico, FIPS 72001, latitude 18.18004, longitude -66.75218, time zone America/Puerto_Rico, and a population of 18,570.

## Assumptions

- The ZIP code you enter is a valid five digit code that exists in the reference table.
- County includes county equivalents such as Louisiana parishes, Alaska boroughs, and Puerto Rico municipios.
- When a ZIP code crosses county lines, the result reports the primary county assigned to the ZIP code's default delivery area.

## Common questions

### How do I look up the county for a ZIP code?

Enter the five digit ZIP code in the field above and the tool returns the county or county equivalent, its FIPS code, central latitude and longitude, time zone, and population in one step.

### Can a ZIP code belong to more than one county?

Yes. Some ZIP codes, especially rural routes and post office box ZIPs, span multiple counties. This lookup reports the primary county, which is the county tied to the ZIP code's default delivery area in USPS records.

### What is a FIPS county code and why does it matter?

A FIPS code is a five digit Federal Information Processing Standards number that uniquely identifies a county. The first two digits are the state or territory and the last three are the county, so 72001 identifies Adjuntas in Puerto Rico. Many government forms and data systems ask for this code instead of the county name.

## Related tools

- /state-fips-lookup-calculator/
- /zip-city-lookup-calculator/
- /zip-time-zone-lookup-calculator/

## Sources

- [Gazetteer Files](https://www.census.gov/geographies/reference-files/time-series/geo/gazetteer-files.html)
- [HUD USPS ZIP Code Crosswalk Files](https://www.huduser.gov/portal/datasets/usps_crosswalk.html)

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