CRS Converter
Transform GeoJSON coordinates between different Coordinate Reference Systems (CRS) and projections.
Coordinate Reference Systems
→
Input GeoJSON
or drag & drop
What is a CRS?
A Coordinate Reference System (CRS) defines how coordinates map to locations on Earth. Different systems optimize for different purposes:
- EPSG:4326 (WGS84) — GPS coordinates (latitude/longitude)
- EPSG:3857 (Web Mercator) — Web maps (Google, Leaflet, Mapbox)
- UTM zones — High-accuracy regional projections
- National grids — Country-specific coordinate systems
How to Use
- Upload GeoJSON or paste coordinates
- Select source CRS (e.g., EPSG:4326)
- Select target CRS (e.g., EPSG:3857)
- Transform and download reprojected GeoJSON
Common Conversions
WGS84 → Web Mercator
EPSG:4326 → EPSG:3857Convert GPS coordinates to web map projection
Web Mercator → WGS84
EPSG:3857 → EPSG:4326Convert web map coordinates back to latitude/longitude
WGS84 → UTM
EPSG:4326 → EPSG:326xx (UTM zones)High-precision regional mapping
Local CRS → WGS84
EPSG:2154 (France) → EPSG:4326
EPSG:27700 (UK) → EPSG:4326
EPSG:3395 (Mercator) → EPSG:4326Features
✓ 500+ CRS supported — All EPSG coordinate systems ✓ Preserve geometry — Maintains topology and attributes ✓ Batch transformation — Convert entire FeatureCollections ✓ Precision control — Set decimal precision for output ✓ Visual preview — See before/after on map ✓ Fast processing — Powered by Proj4js library
Use Cases
🗺️ Web mapping — Convert GPS data to Web Mercator for Leaflet/Google Maps 📊 GIS workflows — Reproject data between different coordinate systems 🛰️ Satellite imagery — Align raster and vector data projections 📍 Field surveys — Convert UTM measurements to GPS coordinates 🌍 International projects — Harmonize data from different national grids
Popular EPSG Codes
| EPSG Code | Name | Description |
|---|---|---|
| 4326 | WGS84 | GPS coordinates (lat/lon) |
| 3857 | Web Mercator | Web maps (Google, OSM) |
| 3395 | World Mercator | Navigation charts |
| 4269 | NAD83 | North America |
| 4258 | ETRS89 | Europe |
| 2154 | Lambert-93 | France |
| 27700 | OSGB 1936 | UK National Grid |
| 32601-32660 | WGS84 UTM North | UTM zones 1N-60N |
| 32701-32760 | WGS84 UTM South | UTM zones 1S-60S |
Tips
💡 Know your source CRS — Check metadata or documentation 💡 Choose appropriate target — UTM for precision, Web Mercator for maps 💡 Mind the distortion — All projections distort area, distance, or shape 💡 Use UTM for measurements — Better accuracy than Web Mercator 💡 Verify after conversion — Check sample coordinates for accuracy
Technical Details
Transformation Engine
- Proj4js — Industry-standard projection library
- EPSG database — Full coordinate system definitions
- Datum transformations — Accurate ellipsoid conversions
Supported Input
- GeoJSON (Feature, FeatureCollection)
- All geometry types (Point, LineString, Polygon, Multi*)
- Coordinate arrays
Output Options
- Reprojected GeoJSON
- Precision control (decimal places)
- CRS metadata in output
Performance
- Client-side processing (no server uploads)
- Fast transformation (<1 second for typical files)
- Handles large datasets (tested up to 50MB)
Related Tools
- Coordinate Formats Converter — Lat/Lon ↔ UTM ↔ MGRS ↔ DMS
- GeoJSON ↔ WKT — Convert to Well-Known Text
- GeoJSON Minifier — Reduce file size after reprojection
Frequently Asked Questions
Q: What's the difference between EPSG:4326 and EPSG:3857? A: EPSG:4326 is lat/lon in degrees (GPS), EPSG:3857 is Web Mercator in meters (web maps).
Q: Why do my coordinates look wrong after conversion? A: Check that you selected the correct source CRS. Wrong source CRS = wrong output.
Q: Can I convert to custom/local coordinate systems? A: Yes, if you have the EPSG code or Proj4 definition string.
Q: Will this work offline? A: Yes, all transformations happen in your browser using Proj4js.
Q: How accurate is the transformation? A: Highly accurate for most use cases. Datum shifts are properly handled.
Q: Can I transform 3D coordinates (with elevation)? A: Yes, Z coordinates are preserved and can be transformed if the CRS supports it.
Q: What if I don't know my source CRS? A: Check file metadata, documentation, or try common ones (4326, 3857). Wrong CRS will produce incorrect results.
Q: Does this handle datum transformations? A: Yes, Proj4js handles datum shifts automatically (e.g., NAD27 → WGS84).