Convert between latitude/longitude and US State Plane coordinates, or any EPSG code with a proj4 definition. Free, private, no account required.
SPCS is a set of over 120 zone-based coordinate systems covering the United States, designed so that within each zone, distortion from the projection stays under about 1 part in 10,000. Surveyors, civil engineers, and local governments use it because it's far more accurate for local measurements than UTM or Web Mercator.
This tool includes primary zones for California, Texas, New York, Florida, Colorado, and Washington, verified against the EPSG registry. For any other US zone, or any other EPSG code entirely, switch to Custom EPSG / proj4 and paste the definition string from epsg.io.
Go to epsg.io/<code>.proj4 — for example epsg.io/2229.proj4 for California Zone 5 in US survey feet — and paste the returned text into the Custom EPSG field.
The built-in State Plane zones use meters (the modern EPSG metric definitions). If you paste a custom proj4 string defined in US survey feet, the X/Y results will be in feet instead — the tool doesn't convert units, it reports whatever unit the projection defines.
Yes, completely. All projection math runs inside your browser using the proj4js library. Nothing is sent to a server.
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