Work out magnetic heading instantly with clear inputs, formula shown and shareable results.
True heading converts to magnetic by removing variation (east variation is subtracted, west variation added — the classic 'east is least, west is best'), and magnetic converts to compass by removing the deviation from the aircraft's compass correction card.
Heading chain
Magnetic = True - variation (east +); Compass = Magnetic - deviation
Aviation results are planning estimates only. Always verify take-off, landing, fuel, weight and balance figures against the certified Aircraft Flight Manual, current performance charts and applicable aviation regulations before flight.
East variation is entered as a positive number and is subtracted from true heading; west variation is negative and therefore adds.
From the compass swing recorded on the aircraft's deviation card. It is caused by the aircraft's own magnetic and electrical fields and changes with heading.