What is a grid bearing?

A grid bearing is measured clockwise from grid north (the vertical grid lines on an OS map) to the line connecting two points. Grid north differs slightly from true north and magnetic north. For compass use, you need to convert the grid bearing to a magnetic bearing.

How do I convert grid bearing to magnetic bearing?

In the UK, magnetic declination is currently about 1-2° west (2026). The mnemonic is "Grid to Mag — Add" for westerly declination. So add the declination to the grid bearing to get the magnetic bearing for your compass. Check the map margin for the current declination value.

How accurate does my bearing need to be?

In good visibility, a bearing accurate to 5° is usually sufficient. In poor visibility, aim for 2° accuracy. Over 1km, a 5° error puts you about 87m off target. Always use attack points, catching features and collecting features as backup navigation techniques.

CampCalcs

Bearing Calculator

Calculate the grid bearing between two OS grid reference points.

Start Point

Easting

5-figure grid ref easting (left-right)

Northing

5-figure grid ref northing (bottom-top)

End Point

Easting

5-figure grid ref easting (left-right)

Northing

5-figure grid ref northing (bottom-top)

How We Calculate This

Grid bearing = atan2(dEasting, dNorthing) converted to degrees (0-360°)

Distance = sqrt(dE² + dN²) in metres (when using metre-based grid references)

Frequently Asked Questions

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Last updated: February 2026

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