EPSG:27700 · Europe
British National Grid (OSGB36) to KML & KMZ
Convert British National Grid (OSGB36) eastings and northings to latitude and longitude, and save them as a Google Earth KML or KMZ. Try a single point here, or convert a whole spreadsheet in the web app.
- Converter already set to EPSG:27700
- Datum shift to WGS 84 applied automatically
- Whole sheets with photos and boundaries in the web or Windows app
About British National Grid (OSGB36)
The British National Grid is the Ordnance Survey grid used across Great Britain, on the OSGB36 datum and the Airy 1830 ellipsoid. The converter uses the published seven-parameter (Helmert) shift to WGS 84, which is good to about 2 m. The official OSTN15 grid transformation, which is more exact, is not bundled.
Where it's used: England, Scotland and Wales: OS mapping, planning drawings, topographic and utility surveys.
Convert a whole spreadsheet
- Open the web app or the Windows app, and paste your rows from Excel or open a CSV file.
- Under Coordinate system, search for “27700” and pick OSGB36 / British National Grid.
- Check one point you know on the map, then press Save KML or Save KMZ (with photos) and open it in Google Earth.
Check points for British National Grid (OSGB36)
Five points inside the area of use of British National Grid (OSGB36), with their latitude and longitude on WGS 84 and their easting and northing in this grid (metres). Enter an easting and northing in the converter above: you should get the latitude and longitude shown, to a few centimetres.
| Point | Latitude | Longitude | Easting | Northing |
|---|---|---|---|---|
| Middle of the area of use | 55.38000° N | 3.49500° W | 305,372.19 | 610,575.63 |
| Towards the north-west | 58.75800° N | 6.79800° W | 122,653.55 | 995,538.50 |
| Towards the north-east | 58.75800° N | 0.19200° W | 504,696.44 | 987,007.04 |
| Towards the south-west | 52.00200° N | 6.79800° W | 70,809.72 | 244,606.18 |
| Towards the south-east | 52.00200° N | 0.19200° W | 524,210.17 | 235,271.84 |
Common mistakes with British National Grid (OSGB36)
- Easting and northing swapped. In British National Grid (OSGB36) the middle of the grid is near easting 305,372.19 and northing 610,575.63. If your easting column holds numbers like 610,575.63, the columns are the wrong way round and every point lands far away: swap them before converting.
- Feet entered as metres. British National Grid (OSGB36) is in metres. Coordinates copied from a drawing in feet must be converted first, or every point moves outwards from the grid's origin.
- Forgetting the datum. British National Grid (OSGB36) is not on WGS 84: published 7-parameter shift (typically 1–2 m). Picking a WGS 84 grid with the same projection instead leaves the points off by that amount.
- Points outside the grid's area. British National Grid (OSGB36) is meant for United Kingdom (UK) - offshore to boundary of UKCS within 49°45'N to 61°N and 9°W to 2°E; onshore Great Britain (England, Wales and Scotland). Isle of Man onshore. Points well outside that area convert with growing error; the converter flags them so you can choose the right grid.
- A local site grid. If every point is off by the same distance and direction, the drawing may be on a local site grid. Calibrate on three or more known control points instead.
Before you rely on it
For centimetre-level agreement with OS mapping, use OSTN15 or calibrate on local control points. Always check one known control point before sending a file out.