OS Grid Reference Converter
Convert GPS coordinates to an Ordnance Survey grid reference, or a grid reference back to latitude and longitude, for walking, climbing, surveying and planning.
About this tool
Type in either box and the other updates. GPS coordinates can be decimal or degrees, minutes and seconds, or a town name. Grid references can be any length, with or without spaces: SH 609 543 (6 figure, a 100 m square), SH6098654375 (10 figure, 1 m) or a plain easting and northing such as 260986, 354375. A short reference describes a square, so the latitude and longitude given is its centre.
Phones and GPS units use the worldwide WGS84 datum, but OS maps are drawn on OSGB36, and the two differ by up to about 120 metres in Great Britain. This converter applies the standard Helmert transformation between them, accurate to around 5 metres, which is fine for navigation. (The previous version skipped this step, so its references could be a field away.) The National Grid covers England, Scotland, Wales and the Isle of Man; Northern Ireland uses the Irish Grid. Your last entries are remembered on this device.