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Grid Magnetic Angle Calculator

This is a grid magnetic angle request form. It will calculate the angle between grid north (British National Grid) and magnetic north at a given location. Please note that it only outputs the correct grid magnetic angle for locations in Great Britain. Ireland uses the Irish National Grid

British National Grid in metres.

British National Grid to nearest 100 m with prefix letters (see Ordnance Survey guide to giving a 6-figure grid reference):

Latitude and Longitude (in decimal degrees, longitude negative if west of Greenwich meridian).

Your postcode in Great Britain.