Grid references/coordinates free conversion tool

We’ve set up this page to assist anyone who needs convert to or from:

Latitude/Longitude to OS Grid (Ordnance Survey Grid also called British National Grid & OSGB on GPS units)
Lat/Long deg/min/sec to Decimal degrees (conventionally used in GPS)
Alpha-numeric BNG to Numeric BNG
OSGB36 datum to WGS84 datum

Such as:

  • Converting ‘Google Maps’ Lat/Long to OS Grid
  • SAR teams who need to call in an air asset (OS Grid to Lat/Long)
  • Aircrew who to convey an air coordinate to a grid reference used on the ground
  • Military personnel to convert BNG to MGRS
  • Police forces which still use the 12 BNG number system
  • Surveyors
  • GPS geocachers

To enter a 6 or 8 figure BNG reference or decimal degrees with less than 6 decimal places simply add zeros as illustrated beneath:

BNG
6 fig: NH 990 059 = NH 99000 05900
8 fig: NH 9901 0597 = NH 99010 05970
10 fig: NH 99015 05977 = NH 99015 05977
Dec Lat Long
2 decimal places 57.13N 03.67W = 57.130000N  03.670000W
4 decimal place 57.1335N 0.3723W = 57.133500N. 03.672300W
12 decimal place 57.133565N 03.670026 = 57.133565N 03.670026W

For all maps produced after May 2014 use the WGS84 datum. Prior to this date use the OSGB36 datum.

To the right of the OS Grid box is the 12 figure numeric OS Grid.

Type OS Grid reference and press enter to see all conversions:

OS Grid Ref ≡

For latitude/longitude, select which type of value you are inputing:

Lat/Lon (WGS84)  
(SW corner of grid square)
Lat/Lon (OSGB36)  
no longer used (since 2014)

The most accurate way to determine a grid reference from a map is to use our Grid Reference Tool.