What Is My Location

OS Grid Reference Finder

Tap once and you get your position as a National Grid reference — TQ 30412 80125 style — at 6, 8 or 10 figures, ready to read to a walking partner or a rescue team. Paste any grid reference and it converts back to coordinates on a map, and place names work too. Everything computes on your device (about ±5 m across Great Britain), and the page keeps working offline once loaded — which is rather the point on a hill.

Why your GPS and OS map disagree — the datum story

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How a grid reference works

The National Grid slices Great Britain into 100 km squares, each named by two letters — TQ holds London, NN holds Ben Nevis, SW holds Land's End. The figures then walk into that square: the first half go east, the second half go north. Each pair of extra figures makes the square ten times smaller — TQ 30 80 (4 figures) is a 1 km square, TQ 304 801 (6 figures) is 100 m, 8 figures is 10 m, and 10 figures is 1 m. A 6-figure reference is the everyday standard: it's what paper-map margins, guidebooks and walking routes use, and it's precise enough to find a stile.

Why your GPS and the map disagree (and what we do about it)

Your phone's GPS speaks WGS84, the global datum. The National Grid is built on OSGB36, a datum fitted to Britain in 1936 — and the two disagree by up to ~120 m, which is why pasting raw GPS numbers into a grid formula puts you in the wrong field. This tool applies the standard Helmert datum transformation, accurate to about ±5 m anywhere in Great Britain — comfortably inside a 6- or 8-figure square. (Ordnance Survey's own OSTN15 correction grid reaches centimeters, but it's a 15 MB dataset — the wrong trade for a page that must load instantly and work offline. If you're doing survey-grade work, use OS tools; if you're navigating, this is plenty.)

Great Britain only — by design of the grid itself

The National Grid covers England, Scotland and Wales (plus a fringe of sea). Northern Ireland and the Republic of Ireland use a different system — the Irish Grid (and its successor ITM) on a different datum — so a position there gets an honest “outside the National Grid” answer here rather than a wrong-looking reference — the Irish grid page covers the whole island, Northern Ireland included. Everywhere else in the world: use UTM/MGRS, the international cousin built on the same Transverse Mercator idea, or plain GPS coordinates.

Reading a reference to a rescue team

UK Mountain Rescue and coastguard teams are trained on grid references — it's the format they expect from walkers. Give the two letters first, always (“Tango Quebec…” if the line is bad), then the figures in pairs, and say how many figures you're giving: “six-figure reference, TQ 304 801.” Without the letters, the figures repeat in every 100 km square in the country. If you're reporting by phone with signal, the emergency location page covers the whole conversation — including what the 999 call already sends automatically.

Frequently asked questions

What do the two letters at the start mean?
They name the 100 km square you're standing in — TQ around London, NN around Ben Nevis, SW in Cornwall. The figures only make sense inside that square, which is why the letters must always be quoted: TQ 304 801 and NN 304 801 are 600 km apart.
How many figures should I use?
Six figures (100 m) is the everyday standard — guidebooks, route cards, and what rescue teams expect. Use eight (10 m) to mark a car park entrance or a cache, ten (1 m) only when you really mean a single spot. More figures than your GPS accuracy is false precision.
How accurate is the conversion?
About ±5 m anywhere in Great Britain. GPS uses the WGS84 datum and the National Grid uses OSGB36; this tool applies the standard Helmert transformation between them, which is comfortably within a 6- or 8-figure square. Survey-grade work should use Ordnance Survey's OSTN15 tools instead.
Does it work in Northern Ireland or Ireland?
No — and neither does the National Grid itself. Ireland uses the Irish Grid and ITM, a separate single-letter system on a different datum, covered by our Irish grid reference page — it works across Northern Ireland and the Republic alike. Positions outside Great Britain get an honest “outside the grid” message here rather than a misleading reference.
Does this page work offline, on a hill with no signal?
Yes. All the mathematics runs on your device and the page is cached after your first visit, so finding and converting grid references needs no connection at all. Only the optional map tiles and place-name search require one.
Related tools
Irish Grid Reference Finder Find your Irish Grid reference and ITM coordinates in one tap — works across Northern Ireland and the Republic — or convert any reference back to a map. UTM Coordinates for My Location See your UTM and MGRS coordinates in one tap, or convert between UTM and latitude/longitude in both directions. WGS84, meter-level accuracy, free, private. Coordinate Converter Convert coordinates between decimal degrees, DMS, DDM, UTM, MGRS, Plus Code and geohash. Paste any format, click the map, get all 8 instantly. GPS Coordinates Get your GPS coordinates now: latitude and longitude in decimal, DMS, UTM, MGRS, Plus Code and geohash. Copy, convert, and share in one tap. How to Share Your Exact Location in an Emergency Get your exact GPS coordinates in one tap and share them by call, text, or maps link — plus what 911/112 sees automatically, and what to do with no signal. WGS84 vs OSGB36: Why Your GPS and Your OS Map Disagree Your phone speaks WGS84; OS maps live on OSGB36. What a datum actually is, why raw coordinates land ~100 m off, and how Helmert and OSTN15 bridge the gap. How to Read a Grid Reference Learn to read and give grid references step by step — eastings before northings, what 4, 6 and 8 figures mean, and how to take one from any paper map.