Lambert 93 ↔ GPS (WGS84) Coordinate Converter
Convert Lambert 93 (RGF93, EPSG:2154) coordinates to GPS latitude/longitude and back — the official French metropolitan projection, free and in your browser.
Lambert 93 is the official projected coordinate system for metropolitan France, defined on the RGF93 geodetic datum and registered as EPSG:2154. Where GPS gives you a latitude and longitude in degrees on a round Earth, Lambert 93 gives you a flat X (easting) and Y (northing) in metres on a Lambert conformal conic projection — which is what IGN maps, the cadastre and most French GIS files actually use.
RGF93 is the French realisation of the modern ETRS89/WGS84 reference frame, so for everyday conversion Lambert 93 and your GPS coordinates describe the same point to within a few centimetres — no datum shift to worry about. The older NTF datum with Lambert II étendu (EPSG:27572) is different: it is tied to the historic Paris meridian and can sit tens to hundreds of metres away, which is why mixing the two is a classic source of error.
A worked example: the Eiffel Tower is 48.8584, 2.2945 in GPS (WGS84) decimal degrees. In Lambert 93 that is X = 648 237 m, Y = 6 862 272 m. Notice the values are large positive numbers in metres — Lambert 93 places a false origin far to the south-west so that every point in France has positive coordinates. If your X looks like ~650 000 and your Y like ~6 800 000, you are almost certainly looking at Lambert 93.
You need Lambert 93 whenever you work with French official data: a cadastral parcel, an IGN BD TOPO export, a town-planning (PLU) shapefile, or survey coordinates from a geometer. Paste your X/Y above to get the GPS position and address; or enter a GPS coordinate to read it back in Lambert 93. Everything runs locally in your browser — nothing is uploaded.
Frequently asked questions
What is Lambert 93?
Lambert 93 (EPSG:2154) is the official projected coordinate system for mainland France, based on the RGF93 datum. It expresses positions as X/Y in metres rather than latitude/longitude in degrees.
What is the difference between Lambert 93 and WGS84?
WGS84 is the global GPS latitude/longitude system in degrees; Lambert 93 is a flat projection in metres for France. Because Lambert 93 uses the RGF93 datum (aligned with WGS84), they describe the same point to within centimetres.
Is RGF93 the same as Lambert 93?
Not exactly. RGF93 is the geodetic datum (the reference frame); Lambert 93 is the map projection built on it. People often say 'Lambert 93' to mean coordinates expressed in that projection on the RGF93 datum.
How do I recognise Lambert 93 coordinates?
They are two large numbers in metres: X (easting) around 100 000–1 300 000 and Y (northing) around 6 000 000–7 200 000 for metropolitan France.
What about Lambert II étendu or the CC zones?
Lambert II étendu (EPSG:27572) is the older NTF projection still found on legacy maps; the CC42–CC50 zones (EPSG:3942–3950) are RGF93 conic zones per latitude band. This tool converts all of them — switch projection in the form above.