Magnetic Variation
Last updated: April 20, 2026 · Maintained by Aviatr Editorial Team
What is Magnetic Variation?
Magnetic variation is the angular difference between geographic (true) north and magnetic north at a specific location, expressed in degrees East or West. Variation changes with location and drifts slowly over years as the Earth's magnetic field shifts; current values are published on aeronautical charts and must be applied to convert between true and magnetic bearings.
TC = MC + VAR (East is least, West is best)How is Magnetic Variation used?
Pilots apply variation every time they convert a chart-plotted true course into a magnetic heading to fly. The mnemonic 'East is least, West is best' means: variation East is subtracted from true to obtain magnetic; variation West is added. Across Europe, variation ranges from roughly 3° East in Germany to near zero in central France and increasing West values toward the Atlantic coast. Aeronautical charts display isogonic lines connecting equal variation values. Runway designations use magnetic bearing, so when variation drifts enough — typically more than half a degree — airports renumber their runways; several major European airports have done so in recent decades. Flight management computers apply variation automatically, but pilots verify the outcome for gross errors. EASA General Navigation theory examinations include variation calculations in true-to-magnetic course conversion problems.