What is an OS Grid Reference?

An Ordnance Survey National Grid reference is the standard way to describe a location in Great Britain. It uses two letters for a 100km square (for example NY in the Lake District) followed by a pair of numbers for the easting and northing. A full 10-figure reference such as NY 21545 07215 pinpoints a spot to within about a metre, which is exactly what Mountain Rescue ask for in an emergency.

How do I convert a grid reference to latitude and longitude?

Type the grid reference into this tool (with or without spaces, for example NY215072 or NY 21545 07215) and it returns the latitude and longitude in WGS84 — the same datum used by Google Maps and most GPS devices. You can also paste a latitude and longitude to get the grid reference back.

Does the converter work without a phone signal?

Yes. All of the maths runs in your browser, so once the page has loaded it works with no signal. Reading your current grid reference uses your phone's built-in GPS, which also works without a mobile signal.

Free Walking Tool

OS Grid Reference Converter

Convert an Ordnance Survey grid reference to latitude & longitude and back, or read your current grid ref straight from your phone's GPS. No account, works offline on the fells.

Enter an OS Grid Reference

With or without spaces — e.g. NY215072, NY 21545 07215, or an all-numeric easting northing like 321545, 507215.

Conversions are approximate (typically within a metre or two for the maths, but your GPS fix may be far less accurate). Always check the result against your map, and never rely on a single tool for navigation or in an emergency. Full disclaimer

Reading a grid reference

A National Grid reference has three parts: two letters for the 100 km square, then an easting (how far right) and a northing (how far up). The more figures, the more precise:

NY — the 100 km square (most of the central and northern Lakes is in NY).
4-figure (NY 21 07) — locates a 1 km square.
6-figure (NY 215 072) — to about 100 m, fine for most walks.
10-figure (NY 21545 07215) — to about 1 m, what Mountain Rescue ask for.

Disclaimer

This converter and all of the values it shows — grid references, latitude and longitude, eastings and northings, and map links — are provided free of charge for general guidance only, on an "as is" basis, and are approximate. They must not be relied upon as a sole or primary means of navigation or as safety advice.

The conversion uses the standard Ordnance Survey transformation between WGS84 and the OSGB36 National Grid. While the underlying maths is generally accurate to within a metre or two, results can still be affected by rounding, by the precision of the reference you enter, and — when reading your current position — by the accuracy of your device's GPS, which can be inaccurate by tens of metres or unavailable, particularly in remote or mountainous areas such as the Lake District.

You should always carry an appropriate map and compass, suitable equipment and supplies, and have the navigation skills and experience needed before setting out. Use of this tool is entirely at your own risk.

To the fullest extent permitted by law, TheLakeDistrict.com accepts no responsibility or liability for any loss, injury, damage, delay, accident or inconvenience arising directly or indirectly from use of this tool or reliance on the information it provides. Nothing in this disclaimer excludes or limits any liability that cannot lawfully be excluded or limited.

Safety on the Fells

The mountains can be dangerous. Weather changes quickly. Be prepared before you set out.

Plan Your Route: Choose a walk that matches your fitness and experience. Check the weather forecast specifically for the mountains (e.g., MWIS).
Tell Someone: Let someone know your route and what time you expect to be back.
Wear the Right Gear: Wear sturdy walking boots with good grip. Pack waterproof layers, a hat, and gloves, even on a sunny day.
Navigate Properly: Carry a map and compass and know how to use them. A fully charged phone with a GPS app is a good backup, but don't rely on it.
Pack Essentials: Take plenty of food and water, a torch (headtorch is best), a first-aid kit, and an emergency whistle and survival bag.
In an Emergency: If you are lost or injured, dial 999 or 112 and ask for Police, then Mountain Rescue. A precise grid reference (a 10-figure one if you can) helps them find you fast.

Essential OS Maps

A physical map and compass are essential for safety and navigation in the fells. These are the four Ordnance Survey Explorer maps that cover the entire Lake District National Park.

Explorer OL4 South-Western Fells Explorer OL5 North-Eastern Fells Explorer OL6 South-Eastern Fells Explorer OL7 North-Western Fells

How It Works

What's an OS Grid Reference?

An Ordnance Survey National Grid reference pinpoints a location in Great Britain using two letters for a 100 km square (such as NY in the Lakes) followed by an easting and a northing. A 10-figure reference like NY 21545 07215 locates a spot to within about a metre — exactly what you'd read out to Mountain Rescue.

What format can I type in?

Anything sensible: with or without spaces (NY215072 or NY 215 072), a full 10-figure ref, or even an all-numeric easting and northing such as 321545, 507215. For latitude and longitude, use decimal degrees in WGS84 — the same numbers Google Maps shows.

Does it work without signal?

Yes. All the maths runs in your browser, so once the page has loaded it works with no signal. The "Use my location" button reads your phone's built-in GPS, which also works without a mobile signal.

How accurate is the conversion?

It uses the standard OS transformation between WGS84 and the OSGB36 National Grid, accurate to within a metre or two — well within the precision of a 10-figure grid reference. When reading your live position, the limiting factor is your GPS, which can be off by tens of metres.