Find ZIP Codes in Radius

• What is a ZIP code radius search
• Anatomy of a US ZIP code
• How to use the tool
• Common search examples
• Typical ZIP density by region
• Use cases & worked examples
• Distance methodology
• How this compares to alternatives
• Limitations & accuracy notes
• Glossary
• Frequently asked questions
• Data sources

What is a ZIP code radius search?

A ZIP code radius searchreturns every US postal code (ZIP) whose geographic center falls within a chosen distance — the "radius" — of a point on the map. The point can be an address, a city, a landmark, your current GPS location, or another ZIP code. The result is the list of ZIPs you can reach, advertise to, deliver to, or analyze inside that circle.

ZIP codes were introduced by the US Postal Service in 1963 as part of a system called the Zone Improvement Plan— that's where the acronym "ZIP" comes from. The original goal was faster mail sorting, not geography. Over time, ZIPs became the de-facto unit for direct marketing, demographic analysis, and service-area definition, even though they were never designed as polygons. To make ZIPs usable for statistics, the US Census Bureau created ZCTAs(ZIP Code Tabulation Areas) — polygons that approximate each ZIP's service area. The boundaries you see on the map above are ZCTAs.

This tool is built around four common questions: (1) Which ZIPs are inside my service area? (2) How many people live there? (3) Which counties do those ZIPs cross? (4) Can I get a clean list to import elsewhere? Every answer is computed in your browser against pre-loaded Census data — there is no server, no API key, no rate limit.

Anatomy of a US ZIP code

A standard US ZIP code has 5 digits, and each digit narrows the geography from broad region down to a small delivery cluster. Understanding what the digits mean helps explain why ZIPs near each other often share their first 2 or 3 numbers.

Some ZIPs do not represent a geographic area at all. Unique ZIPs are assigned to a single high-volume address — universities, hospitals, or government buildings — and have no boundary. PO Box ZIPs serve only post office boxes. Both will appear in lookups but show zero population.

How to use this tool

Common search examples

The numbers below come from real searches in this tool — useful as a sanity check for what to expect when you enter a major city. Counts vary slightly with each Census refresh.

Typical ZIP density by region type

ZIP density tracks population density. A 25-mile radius in midtown Manhattan will return roughly 30× as many ZIPs as the same radius in rural Nebraska. Use this table to set realistic expectations and pick a radius that actually returns useful results for your area.

Who uses ZIP code radius search

1. Direct mail and EDDM campaigns

Businesses target direct mail to households within a specific distance of their location. A restaurant might mail menus to all ZIPs within 5 miles; a car dealership might target 25. The population data helps estimate mailing costs, and the CSV imports straight into USPS Every Door Direct Mail (EDDM) tools.

2. Franchise territory definition

Franchisors use ZIP-code radii to define exclusive territories so franchisees don't compete with each other. A 15-mile radius around each location creates a defensible boundary that maps cleanly to mailing lists, ad targeting, and lead routing.

3. Healthcare service area analysis

Hospitals and clinics use ZIP-level service-area definitions for Medicare/Medicaid reporting, expansion planning, and patient acquisition modeling. CMS programs often require ZIP-coded reporting of where patients live.

4. Real estate market analysis

Agents and investors use ZIP radii to define comparable-sales areas, analyze inventory, and identify expansion neighborhoods. The county data is useful for tax-jurisdiction analysis since property tax rules change at county lines.

5. Delivery and service area planning

Restaurants, courier services, HVAC contractors, and home-services businesses use ZIP radii to define where they will and won't deliver. The CSV plugs directly into e-commerce shipping rules, scheduling software, and routing platforms.

6. Political campaigns and canvassing

Local campaigns plan door-to-door canvasses, mailers, and phone banks by ZIP. A radius search around a candidate's home base or a key issue location surfaces the priority ZIPs for organizing.

7. Site selection and competitor mapping

Retailers picking a new location pull ZIP-radius population data for each candidate site to compare addressable markets. The list also feeds into cannibalization analysis — how much demand does a new store pull from existing locations within 5–15 miles?

8. Data science and ML feature engineering

Data teams use ZIP radius lookups to build location features — "count of nearby ZIPs by population", "median income within 10 mi", etc — for churn models, fraud detection, and recommendation systems.

How the distance calculation works

The tool uses the Haversine formula to compute great-circle distance between the center point and each ZIP code centroid. This is the shortest path between two points on the surface of a sphere — the same math airplanes use.

a = sin²(Δφ/2) + cos(φ₁) · cos(φ₂) · sin²(Δλ/2)
c = 2 · atan2(√a, √(1−a))
d = R · c            // R = 3959 mi (Earth radius)

Each ZIP is represented by a single coordinate: its population-weighted centroidfrom the SimpleMaps US ZIPs database. Distances are measured to that centroid, not to the nearest edge of the ZIP polygon. For most uses this is what you want — it answers "is the typical resident of this ZIP within my radius?" rather than "does any sliver of this ZIP cross my radius?".

Inclusion is binary: a ZIP is either in your radius or it isn't. A ZIP whose centroid is 50.1 mi from your point will be excluded from a 50 mi radius even if most of its area falls inside. Tighten or loosen the radius slightly if you need edge cases captured.

The visible circle on the map is rendered as a true geodesic polygon (Turf.js, 80 vertices), so it respects Earth's curvature. At small radii the difference is invisible. At 200+ miles or near the poles, a flat-projection circle would visibly distort — the geodesic version does not.

How this compares to alternatives

ZIP code radius lookups exist in several other tools and services. Here's an honest side-by-side so you can pick the right one for your job.

Limitations & accuracy notes

We're upfront about what this tool does and doesn't do. Knowing the limitations helps you avoid the classic mistakes when working with ZIP-based geography.

• ZCTAs are approximations.A ZCTA polygon is the Census Bureau's best guess at a USPS service boundary. The two are not identical, and both can change without notice.
• Centroid-based inclusion misses edges. A large rural ZIP can extend many miles past its centroid. If you need every address within a precise distance, use a drive-time isochrone tool instead.
• Population is annual, not real-time. Census ACS estimates lag by 1–3 years. Use this tool for planning, not for legal or compliance reporting that requires the latest data.
• Boundaries are simplified. Polygons are simplified to ~330 m tolerance for fast browser rendering. Coastline detail and small islands may be reduced. The original Census shapefiles are higher fidelity if you need cartographic accuracy.
• Not all ZIPs have boundaries. Unique ZIPs (single buildings) and PO Box ZIPs have no polygon. They show up in the results table when their point falls inside the radius, but no shape is drawn on the map.
• The radius is straight-line, not driving distance. A ZIP 10 miles away as the crow flies might be a 25-minute drive in city traffic. Use a drive-time tool for delivery routing.

Glossary

ZIP Code

A 5-digit postal routing code introduced by the US Postal Service in 1963. ZIP stands for "Zone Improvement Plan." About 41,000 ZIP codes exist; not all represent geographic areas.

ZCTA

ZIP Code Tabulation Area — a polygon approximating a USPS ZIP code, created by the US Census Bureau for statistical reporting. ZCTAs are what most "ZIP code maps" actually show.

ZIP+4

A 9-digit extension that pinpoints a city block, building, or single delivery point. Not used for geographic radius searches.

Unique ZIP

A ZIP assigned to a single high-volume address (e.g., a university, hospital, or government building). Has no geographic area, often shows zero residential population.

PO Box ZIP

A ZIP that only serves a post office box facility. No assigned area or resident population.

Population-weighted centroid

The "average" location of all residents inside a ZIP, weighted by where they actually live. More accurate for service-area analysis than the geometric center.

Haversine distance

Great-circle distance between two points on a sphere. Used for accurate distance calculation over the curved surface of the Earth.

EDDM

Every Door Direct Mail — USPS service for sending mail to every address on a postal route, often defined by ZIP. CSV exports from this tool can be used to plan EDDM campaigns.

Related tools and resources

For visualizing the radius on a map without ZIP code data, use the Map Radius Tool — it works worldwide and supports multiple circles with different colors.

If you need the total population within a radius (not broken down by ZIP code), the Population Within Radius tool calculates aggregated demographics for any circular area.

To find cities instead of ZIP codes, use Find Cities in Radius — it lists all cities and towns within your specified distance with population data.

If you're not sure what ZIP code you're currently in, the What ZIP Code Am I In? tool uses GPS or address lookup to identify your postal code instantly with the ZCTA boundary drawn on the map.

Browsing by state? Each state has a county directory with population, area, and interactive county map:

Frequently asked questions

ZIP code coordinates, population, county, and city from SimpleMaps US ZIP Codes Database, derived from US Census Bureau ZCTA definitions and the American Community Survey (ACS). ZCTA boundary polygons from the OpenDataDE State ZIP Code GeoJSON project (US Census 2020 ZCTA shapefiles), simplified with ogr2ogr -simplify 0.003 for fast browser rendering. Address autocomplete uses the Photon geocoder with OpenStreetMap data. Reverse geocoding uses Nominatim. Distances use the Haversine great-circle formula. Map rendering uses MapLibre GL JS with OpenFreeMap tiles and Turf.js for the geodesic radius polygon.