ZIP code radius finder

Distances here are straight lines between ZIP centroids, computed with the haversine formula over a mean Earth radius of 6,371.0088 km. They are not driving distances; a road between the same two points often runs a fifth to half as long again. Membership is centroid based too, so a large rural ZIP whose area overlaps the circle still stays out when its centroid sits outside it, and PO box codes can share one centroid with their parent town. The bundled GeoNames US snapshot (CC BY 4.0, snapshot 2026-10-31) is a capped sample dense around New York with one or two anchors elsewhere, so a small circle in an unlisted town can come back empty; absence from this list does not mean the ZIP does not exist. Center ZIP codes sharing a centroid with their neighbours appear tied at the top. Everything runs in this tab; nothing is uploaded.