OS grid reference converter
Convert between an OS grid reference, eastings and northings, and WGS84 latitude and longitude, for anywhere in Great Britain.
Free, no sign-in. Nothing you type is stored or sent anywhere — it's all worked out in your browser.
Accurate to a few metres — not for setting out.
Enter a location in Great Britain.
How this works
Grid references are split into the 100 km square letters and the easting/northing figures. Coordinates are converted between OSGB36 (the National Grid) and WGS84 (GPS) with the standard Helmert 7-parameter shift.
Accurate to a few metres — not for setting out. For setting out, use OSTN15 through your survey software.
FAQs
What is an OS grid reference?
A location on the Ordnance Survey National Grid: two letters for the 100 km square, then equal numbers of easting and northing figures. 10 figures give 1 m, 8 give 10 m and 6 give 100 m.
How accurate is this converter?
To within a few metres. It uses the standard 7-parameter OSGB36 datum shift, not OSTN15. Don't use it for setting out.
Can I convert eastings and northings to latitude and longitude?
Yes. Choose 'Eastings / northings', enter them in metres, and the tool shows the grid reference and the WGS84 lat/long.
Does it work in Northern Ireland?
No. Northern Ireland uses the Irish Grid, which this tool doesn't cover. It works for Great Britain.
Civvio works this out automatically from your contract and site records.
Upload the contract and keep your diary, and Civvio flags the dates, notices and money at risk on every job — for you to review before anything is sent.
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