How does one calculate the magnetic heading from a true heading?

To calculate the magnetic heading from a true heading, the correct process involves adjusting the true heading with the magnetic variation. Magnetic variation, or magnetic declination, is the angle difference between true north (geographic north) and magnetic north (the direction a magnetic compass points). This adjustment is critical because compasses rely on the Earth’s magnetic field, which can differ significantly from true north depending on your geographic location.

When determining magnetic heading, if the magnetic variation is east, the true heading is decreased by the magnetic variation. Conversely, if the magnetic variation is west, the true heading is increased by the magnetic variation. This adjustment allows pilots to convert their navigation from the true heading, which is based on global geographic coordinates, to the magnetic heading that their compass will indicate. Understanding this relationship is vital for accurate navigation, especially during flight planning and in-flight maneuvers where precise headings are crucial for both safety and efficiency.