Magnetic Declination and True Bearing
A magnetic compass points toward magnetic north, which differs from true (geographic) north by an angle called magnetic declination that varies by location and slowly changes over time. Given a known local declination, true bearing = magnetic bearing + declination (using the convention that east declination is positive and west declination is negative), normalized to 0–360°.
Because declination depends on your exact location and the current date (it’s typically obtained from a magnetic model like the World Magnetic Model or a local topographic map/chart), this calculator lets you enter your own known declination value rather than calculating it directly. Always use an up-to-date declination figure for your specific location for accurate navigation.