UK Grid Reference Finder
Turn your phone’s GPS position into an accurate OS grid reference and OSGB36 coordinates, using the full OSTN15 model. Works offline, free, with no ads and no accounts.
What it does
- OS grid references, OSGB36 eastings and northings, WGS84, MGRS, Plus Codes, Irish Grid and postcodes
- Full OSTN15 transformation built in (0.15 m at 95%), so it works without a signal
- Compass showing magnetic, true and grid north, plus a spirit level
- Available in 14 languages
- Free, with no ads, no accounts and no tracking
Why accuracy matters
Most apps that convert GPS positions to British National Grid use a single Helmert transformation. That’s fine for finding your way, but it isn’t accurate enough for survey work. According to Ordnance Survey, a single Helmert transformation from ETRS89 to OSGB36 can be out by up to 3 m (95%) in plan and 3.5 m (95%) in plan and height, depending on where you are in the country. In our own tests we’ve seen errors of up to 10 m in other apps.
UK Grid Reference Finder uses the OS OSTN15 transformation model instead, so it gives full 10-figure grid references and matches all of the Ordnance Survey test coordinates. For the details, see the Ordnance Survey document A Guide to Coordinate Systems in Great Britain.
Read the UK Grid Reference Finder privacy policy.