About gridref

gridref.org.uk is a free, fast converter for British grid references, built to work well on a phone with a weak signal. Type a grid reference, coordinates, a postcode or a place name and you get the same point in every common format, on a map.

How conversions work

Grid references are converted to and from latitude/longitude with the open-source geodesy library by Chris Veness (MIT licence). It uses a Helmert transformation between the OSGB36 and WGS84 datums, accurate to a few metres. All conversions happen in your browser.

Where the data comes from

• Postcode district and sector centres are calculated from Code-Point Open, released as OS OpenData under the Open Government Licence. Each centre is the average position of every postcode in that district or sector. Northern Ireland postcodes aren’t included because Northern Ireland uses the Irish grid.
• Summits come from The Database of British and Irish Hills v18.6, licensed under CC BY 4.0. We include Munros, Corbetts, Wainwrights, Hewitts, Nuttalls, Marilyns and the Welsh 3000s in England, Scotland and Wales.
• Postcode and place search in the converter uses postcodes.io, a free, open postcode API.
• Maps are from OpenStreetMap, built by volunteers.

Independence

gridref.org.uk is an independent site. It is not affiliated with or endorsed by Ordnance Survey, Royal Mail or any emergency service.