How to read a grid reference
A grid reference such as NN 166 712, the summit area of Ben Nevis, has three parts. The two letters name a 100 km square. The first group of digits is the easting, read left to right along the bottom of the map; the second is the northing, read bottom to top. Always read along the corridor, then up the stairs.
| Reference | Example | Pinpoints a square of |
|---|---|---|
| 4-figure | NN 16 71 | 1 km, one grid square on an OS map |
| 6-figure | NN 166 712 | 100 m, the usual reference for walkers |
| 8-figure | NN 1666 7126 | 10 m, a building or a gate |
| 10-figure | NN 16667 71262 | 1 m, as precise as a GPS fix |
Eastings and northings to latitude and longitude
Planning applications, surveys and many council and environmental datasets give positions as full eastings and northings, such as 530080, 180337 near Charing Cross. Paste both numbers into the box, separated by a comma or a space, to get the GPS latitude and longitude and the matching grid reference. These are British National Grid values, not UTM: UTM eastings and northings use a different projection and origin, and are converted on the coordinates converter.
When grid references are used
- Hill walking and mountain rescue: giving a 6 or 8-figure grid reference tells rescuers exactly where you are on their OS map. In an emergency call 999 and ask for the police, then mountain rescue.
- Ordnance Survey paper and digital maps, from Explorer and Landranger sheets to OS Maps.
- Planning, environmental and archaeological records, which usually store positions as eastings and northings.
- Scouts, Duke of Edinburgh and geography fieldwork, where 4 and 6-figure references are taught first.