OSGB36 National Grid to Lambert 93 Coordinate Converter
Free online tool to convert coordinates from OSGB36 / British National Grid (EPSG:27700) to RGF93 / Lambert-93 (France mainland) (EPSG:2154). Professional-grade accuracy using proj4, zero install, runs in your browser.
About OSGB36 National Grid
OSGB36 / British National Grid (EPSG:27700). Ordnance Survey Great Britain 1936 datum — the national grid system for England, Scotland and Wales. Universally used in UK survey and cadastre.
About Lambert 93
RGF93 / Lambert-93 (France mainland) (EPSG:2154). The official projection of metropolitan France since 2000. Covers all mainland France + Corsica in a single system with minimal distortion.
Frequently Asked Questions
What is the difference between OSGB36 National Grid and Lambert 93?
OSGB36 National Grid (EPSG:27700) is national grid and based in UK, while Lambert 93 (EPSG:2154) is national grid based in France. Ordnance Survey Great Britain 1936 datum — the national grid system for England, Scotland and Wales. Universally used in UK survey and cadastre. In contrast, the official projection of metropolitan france since 2000. covers all mainland france + corsica in a single system with minimal distortion.
Is this conversion accurate for surveying?
Yes. The conversion uses the industry-standard proj4 library with full datum shift parameters (including seven-parameter Helmert transformation for OSGB36 National Grid). Typical accuracy is sub-meter for civilian applications. For cadastral precision, always verify against the official agency datum.
What coordinate format should I use?
For OSGB36 National Grid, enter coordinates as easting, northing in meters (e.g. 514500, 5033880). The tool auto-detects the format.
Can I convert many points at once?
Yes, use our batch CSV converter. Upload a CSV with your points, select the transformation, download the converted file. Free with a SurveyingPedia account.
Is there an API?
Yes — call /api/v1/transform?from=EPSG:27700&to=EPSG:2154&coords=lat,lng for programmatic access. It returns the transformed coordinates as JSON.