OSGB36 National Grid to WGS84 Coordinate Converter
Free online tool to convert coordinates from OSGB36 / British National Grid (EPSG:27700) to World Geodetic System 1984 (lat/lng) (EPSG:4326). 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 WGS84
World Geodetic System 1984 (lat/lng) (EPSG:4326). The global reference system used by GPS, Google Maps and virtually all modern navigation. Defined by satellite geodesy and continuously refined.
Frequently Asked Questions
What is the difference between OSGB36 National Grid and WGS84?
OSGB36 National Grid (EPSG:27700) is national grid and based in UK, while WGS84 (EPSG:4326) is geographic based in Global. 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 global reference system used by gps, google maps and virtually all modern navigation. defined by satellite geodesy and continuously refined.
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:4326&coords=lat,lng for programmatic access. It returns the transformed coordinates as JSON.