ZIPs Within Radius

Finding every US ZIP code within a specific radius of a center ZIP code is one of the most powerful geographic operations for marketing, logistics, territory analysis, healthcare planning, and competitive intelligence. Our ZIPs Within Radius tool accepts a center ZIP code and a distance in miles or kilometers, then returns every ZIP code whose centroid falls within that circle — giving you an instantly usable geographic target list sorted by distance from your center point.

How Radius Search Works

The tool calculates the Haversine formula straight-line (great-circle) distance from the centroid of your center ZIP code to the centroid of every other ZIP code in the database. The Haversine formula accounts for the curvature of the Earth:

a = sin²(Δlat/2) + cos(lat₁) × cos(lat₂) × sin²(Δlon/2) d = 2R × arcsin(√a)

Where R = 3,958.8 miles (or 6,371 km), Δlat = lat₂ − lat₁, and Δlon = lon₂ − lon₁ (all values in radians). This computation runs against all 42,000+ ZIP codes in the database and returns matching ZIPs sorted by distance in under a second.

Formula: Is a ZIP Within the Radius?

For any candidate ZIP with centroid (lat₂, lon₂) and center ZIP centroid (lat₁, lon₁): compute d using the Haversine formula. If d ≤ your specified radius r, the ZIP is included. The result set is sorted ascending by d so the closest ZIPs appear first. This enables "nearest N ZIP codes" queries by taking the top N results regardless of radius.

Choosing the Right Radius

The appropriate radius depends on your use case and geography. 5–10 miles is appropriate for hyper-local service businesses (plumbers, electricians, restaurants, urgent care clinics) where customers are rarely willing to travel more than 15 minutes. 15–25 miles suits local delivery services, brick-and-mortar retail trade areas, and suburban commute zones. 30–50 miles covers regional service companies, day-trip leisure destinations, and regional franchise territories. 50–100 miles is appropriate for multi-county market regions, distribution center service areas, and regional broadcast markets. 100–250 miles captures DMA (Designated Market Area) scale geographies and major regional distribution networks.

Urban vs. rural dramatically affects results: a 10-mile radius in Manhattan returns 80–120 ZIP codes (because ZIPs are tiny and densely packed). The same 10-mile radius in rural Montana may return 3–8 ZIP codes (because each ZIP covers a vast area). Always check result count before using in a campaign to avoid surprising under- or over-coverage.

Using Radius Results for Direct Mail

Direct mail campaigns use ZIP lists as the fundamental targeting unit. Building a mailing list "within 20 miles of our new store at ZIP 30301" means running a ZIPs-within-radius query centered on 30301 with a 20-mile radius and mailing to every household in the resulting ZIP list. List brokers and Every Door Direct Mail (EDDM) through USPS both accept ZIP code target lists. Combining radius-based ZIP selection with demographic filtering (income, age, homeownership) from our ZIP Code Population data creates highly targeted, efficient campaigns.

Ad Platform Targeting

Google Ads, Facebook/Meta Ads, Snapchat, and most programmatic ad platforms accept ZIP code target lists. Building a radius campaign manually (drawing a circle on the platform map) is imprecise — the circle may include ZIP codes partially, with unclear billing implications. Building an explicit ZIP list from a radius query gives you precise, known coverage: every ZIP in your list is fully included, and no ZIP outside your intended area is accidentally included. This is especially important for compliance-sensitive industries (finance, insurance, healthcare) where targeting must be precisely documented.

Logistics and Last-Mile Delivery

Delivery operations define service areas as all ZIP codes reachable within a target drive time or distance from a warehouse or distribution center. A ZIPs-within-radius query centered on the distribution center ZIP with the maximum delivery distance as the radius generates the initial candidate service area. This list is then refined by drive-time analysis to exclude ZIPs that are within the straight-line radius but require much longer driving routes due to geographic barriers (mountains, rivers, bridges).

Healthcare Service Area and Catchment Analysis

Hospitals, health systems, and federally qualified health centers define their service areas — the geographic region from which they draw patients — using radius-based approaches. CMS (Centers for Medicare and Medicaid Services) uses service area ZIP codes for network adequacy assessments and rural health designation purposes. A ZIPs-within-radius query centered on a clinic ZIP provides the candidate service area ZIP list for further analysis against population and provider data.

Competitive Intelligence

Understanding which ZIP codes fall within a competitor's trade area is valuable for targeting counter-programming. If a competitor is located at ZIP 60601, running a 5-mile radius query reveals all ZIPs in their likely trade area. Cross-referencing with your own customer data shows which of those ZIPs you have already penetrated and which represent untapped competitive opportunity adjacent to the competitor's stronghold.