Zip Code to Latitude/Longitude APIs

Two free options for converting US zip codes to coordinates, no API key required.

Option 1: Zippopotam.us (Recommended)

The simplest option - purpose-built for zip code lookups. No authentication, no rate limits documented, CORS enabled.

Base URL

code

https://api.zippopotam.us

Endpoint Format

code

GET /us/{zip_code}

Example CURL

bash

curl "https://api.zippopotam.us/us/90210"

Response Format

json

{
  "post code": "90210",
  "country": "United States",
  "country abbreviation": "US",
  "places": [
    {
      "place name": "Beverly Hills",
      "longitude": "-118.4065",
      "state": "California",
      "state abbreviation": "CA",
      "latitude": "34.0901"
    }
  ]
}

Extracting Coordinates with jq

bash

# Get latitude
curl -s "https://api.zippopotam.us/us/10001" | jq -r '.places[0].latitude'

# Get longitude
curl -s "https://api.zippopotam.us/us/10001" | jq -r '.places[0].longitude'

# Get both as comma-separated
curl -s "https://api.zippopotam.us/us/10001" | jq -r '.places[0] | "\(.latitude),\(.longitude)"'

Response Fields

Field	Description
`post code`	The zip code queried
`country`	Full country name
`country abbreviation`	2-letter country code (US)
`places`	Array of locations (usually 1 for zip codes)
`places[].place name`	City/town name
`places[].state`	Full state name
`places[].state abbreviation`	2-letter state code
`places[].latitude`	Latitude as string
`places[].longitude`	Longitude as string

Notes

•Returns 404 for invalid zip codes
•Coordinates are returned as strings, convert to float if needed
•Data sourced from GeoNames
•Some zip codes may have multiple places in the array

Option 2: OpenStreetMap Nominatim

More powerful geocoding API, but requires a User-Agent header and has rate limits.

Base URL

code

https://nominatim.openstreetmap.org

Endpoint Format

code

GET /search?postalcode={zip}&country=USA&format=json

Example CURL

bash

curl -H "User-Agent: MyApp/1.0 (contact@example.com)" \
  "https://nominatim.openstreetmap.org/search?postalcode=90210&country=USA&format=json"

Response Format

json

[
  {
    "place_id": 123456,
    "licence": "Data © OpenStreetMap contributors, ODbL 1.0.",
    "lat": "34.0901",
    "lon": "-118.4065",
    "display_name": "90210, Beverly Hills, Los Angeles County, California, United States",
    "type": "postcode",
    "importance": 0.435
  }
]

Extracting Coordinates with jq

bash

curl -s -H "User-Agent: MyApp/1.0" \
  "https://nominatim.openstreetmap.org/search?postalcode=10001&country=USA&format=json" \
  | jq -r '.[0] | "\(.lat),\(.lon)"'

Important Requirements

Requirement	Details
User-Agent	Required - Must identify your application
Rate Limit	Max 1 request per second
No Bulk Queries	Cannot download complete lists of postcodes

When to Use Nominatim

•Need additional address details
•Need international postal codes beyond Zippopotam coverage
•Building an application that also needs general geocoding

Comparison

Feature	Zippopotam.us	Nominatim
API Key	Not required	Not required
User-Agent	Not required	Required
Rate Limit	None documented	1 req/sec
US Coverage	43,624 zip codes	Comprehensive
Response	Simple JSON	Detailed JSON
Best For	Simple zip lookups	General geocoding

Recommendation

Use Zippopotam.us for simple US zip code to lat/long conversion. It's simpler, has no documented rate limits, and returns a clean, predictable response format.

Use Nominatim if you need additional geocoding capabilities beyond zip codes, or need the extra address details in the response.