British National Grid → WGS 84

British National Grid to latitude and longitude converter

Convert British National Grid eastings and northings to WGS 84 latitude and longitude, with input examples, coverage and OSTN15 accuracy notes.

Batch coordinate converter

Enter one British National Grid coordinate per line as easting, northing.

Input example: 530028, 180380

0 of 100 coordinates

Results use: latitude, longitude order.

Output example: 51.5072, -0.1276

Numeric coordinates are rounded for display: decimal latitude/longitude to up to 6 decimal places, metre-based coordinates to up to 3, DMS seconds to up to 2, and DDM minutes to up to 4.

About this conversion

Convert British National Grid (EPSG:27700) eastings and northings to WGS 84 using the high-accuracy OSTN15 transformation for Great Britain.

Frequently asked questions

What input is accepted?

Enter British National Grid easting followed by northing, both in metres. Use numeric EPSG:27700 values rather than a two-letter OS Grid Reference.

What output will I receive?

By default, results show WGS 84 latitude first and longitude second in decimal degrees. Select Reverse coordinate order to show longitude first. Displayed decimal places do not add accuracy to the source.

Which axes and units are used?

British National Grid input uses easting then northing in metres. WGS 84 output defaults to latitude then longitude in degrees.

How are precision and datum handled?

The conversion requires OSTN15 and does not fall back to a lower-accuracy transformation. Result quality is still limited by the precision and accuracy of the source grid coordinates.

Where can I use this coordinate system?

British National Grid is for Great Britain. Locations outside its valid transformation area are rejected rather than extrapolated.

What should I check?

  • Enter numeric eastings and northings rather than an OS Grid Reference such as TQ 30028 80380.
  • Check that easting appears before northing.
  • Use coordinates from the British National Grid area in Great Britain.

Is this the same input as an OS Grid Reference?

No. This route uses full numeric eastings and northings in EPSG:27700.

Why is OSTN15 required?

It provides the high-accuracy transformation between WGS 84 and the national grid.