Magnetic Declination Calculator

Magnetic declination is the horizontal angle between magnetic north, where a compass needle points, and true north, the direction of the geographic North Pole. The value depends on location and date. It can be east, west, or close to zero.

This calculator uses the navigation convention that east declination is positive and west declination is negative. If the local value is +8°, magnetic north lies 8° east of true north. The correction matters when you transfer bearings between a magnetic compass and a map referenced to true north.

Declination is a regional model value. Steel, electrical equipment, vehicles, buildings, and magnetic rock can distort a compass at one spot without changing the calculated regional field.

The World Magnetic Model describes Earth's main magnetic field with spherical-harmonic coefficients. NOAA's National Centers for Environmental Information and the British Geological Survey produce the model for United States and United Kingdom defence and navigation agencies.

The bundled WMM-2025 coefficients represent the field at the 2025 epoch and include annual rates of change. The code evaluates those coefficients for latitude, longitude, altitude, and date in your browser. The official model window runs from 2025 through 2030; results outside it are extrapolations and the tool displays a warning.

Earth's field changes because motion in the liquid outer core changes the magnetic field over time. The model's secular variation estimates that gradual drift. Short-lived space-weather disturbances and small local anomalies are outside the main-field model.

Declination can differ substantially between regions and changes fastest in some high-latitude areas. A correction copied from another city may be unsuitable. Use your actual coordinates or enter the map location where the bearing will be used.

The result also includes inclination, the angle the field points into or out of the horizontal plane, plus total, horizontal, and vertical field strength in nanoteslas. A weak horizontal field makes compass direction less stable, especially near magnetic poles.

Find coordinates with My Location, then compare the result on the live compass. For a visual explanation, read magnetic north, true north, and grid north.

To convert magnetic bearing to true bearing, add signed declination and normalize the result to 0–360°. With +8° declination, a 45° magnetic bearing becomes 53° true. With −8° declination, the same magnetic bearing becomes 37° true.

To convert true bearing to magnetic bearing, subtract signed declination. The calculator displays both operations from one input so you can verify the direction. Always check whether a map, device, runway, trail instruction, or survey uses magnetic, true, or grid north before applying a correction.

The Qibla direction finder uses true bearing for the great-circle route to Mecca and derives the magnetic bearing using this same model. The sun compass uses true north because celestial azimuth is independent of magnetism.