How do OS grid references work?

Ordnance Survey grid references use eastings (horizontal) and northings (vertical) measured in metres from the south-west corner of the grid. A 6-figure reference (e.g. 456 789) locates a 100 m square. An 8-figure reference (e.g. 4567 7891) locates a 10 m square.

What is the difference between straight-line and walking distance?

Straight-line (as the crow flies) distance is always shorter than walking distance. Actual walking distance typically adds 20-40% depending on terrain, path availability and obstacles. Use this calculator for map planning, then add extra for the walking route.

How do I read a grid reference from a map?

Remember: along the corridor, up the stairs. Read the easting (horizontal) first, then the northing (vertical). For a 6-figure reference, the first 3 digits are the easting and the last 3 are the northing.

A bearing is the clockwise angle in degrees from grid north. 0° is north, 90° is east, 180° is south, 270° is west. This is a grid bearing; for a magnetic bearing you need to apply magnetic declination.

CampCalcs

Grid Reference Distance Calculator \u2014 OS Distance & Bearing

Calculate straight-line distance and bearing between two OS grid references.

Easting 1

First grid reference easting

Northing 1

First grid reference northing

Easting 2

Second grid reference easting

Northing 2

Second grid reference northing

How We Calculate This

This calculator finds the straight-line distance and bearing between two OS grid references using Pythagoras and trigonometry.

How it works

Grid references are converted to metres, then the distance is calculated using the Pythagorean theorem. The bearing is calculated using the arctangent of the easting and northing differences. Results are given in metres, kilometres and miles.

Frequently Asked Questions

Related Calculators

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Calculate the bearing between two grid references or coordinates.

Pace Counter Calculator

Calibrate your pace count for accurate distance measurement on foot.

Walking Time Calculator

Estimate walking time using Naismith's rule with Tranter's corrections for fitness.

Last updated: March 2026

All calculations are estimates. Always verify conditions and use proper safety equipment outdoors.