Magnetic Declination Calculator

Magnetic declination (sometimes called magnetic variation) is the angle between magnetic north (the direction the north end of a compass needle points) and true north (the direction to the geographic North Pole). This angle varies depending on your location on Earth and changes over time due to the shifting of the Earth's magnetic field. Declination is expressed in degrees east or west of true north. If the declination is positive or east, magnetic north is east of true north. If it's negative or west, magnetic north is west of true north.

This calculator provides an approximation of magnetic declination for educational purposes only. For the most accurate declination values, you should consult the official World Magnetic Model (WMM) or use dedicated navigation tools like NOAA's Magnetic Field Calculator. The real-world magnetic field is complex and influenced by local anomalies that cannot be fully captured in a simplified calculator. If you're using declination for actual navigation purposes, always refer to official and up-to-date sources.

Magnetic declination changes over time because the Earth's magnetic field is constantly shifting. This phenomenon, known as secular variation, is caused by the movement of molten iron in the Earth's outer core, which generates the magnetic field. The magnetic north pole itself moves about 55-60 kilometers per year, and its movement isn't consistent in speed or direction. This means that declination values published on maps become outdated after several years. The rate of change varies by location—some areas experience rapid changes in declination (up to 0.5 degrees per year), while others change more slowly.

To adjust for magnetic declination, you can use either of these methods:

1. Mathematical adjustment: If your declination is east, subtract it from your compass reading to get true bearing. If your declination is west, add it to your compass reading. You can remember this with the phrase "East is least, West is best" (referring to the mathematical operation).
2. Physical adjustment: Many advanced compasses have a declination adjustment screw or ring that allows you to mechanically adjust the compass so it points to true north. Consult your compass manual for specific instructions.

For example, if you're in a location with a declination of 14° East, and your compass reads 60°, then the true bearing would be 60° - 14° = 46°.

The magnetic north pole is not fixed and moves over time due to changes in the Earth's magnetic field. As of 2021, the magnetic north pole was located in the Arctic Ocean, approximately at 86.5°N 164.0°E, near the Severnaya Zemlya archipelago of Russia. However, it has been moving rapidly from Canada's Arctic region toward Siberia at a rate of about 55-60 kilometers per year. This is significantly faster than its historical movement rate. Scientists from the National Oceanic and Atmospheric Administration (NOAA) and the British Geological Survey periodically update the World Magnetic Model to track these changes and provide accurate magnetic field information for navigation.

The agonic line, where magnetic declination is zero, moves over time because it represents the boundary where magnetic north and true north align perfectly. As the Earth's magnetic field changes and the magnetic north pole shifts position, this line of zero declination also shifts. The movement of the agonic line reflects the dynamic nature of the Earth's magnetic field, which is generated by the flowing liquid iron in the outer core. Currently, the agonic line runs through the Americas, from Canada down through the eastern United States and into South America. In the past, it has crossed through different parts of the world. The shifting of the agonic line is one manifestation of the ongoing changes in the Earth's complex magnetic field, which scientists monitor to update navigational references.

Yes, magnetic declination can be exactly zero at locations along the agonic line. The agonic line is a curve on the Earth's surface where magnetic north and true north align perfectly, making the compass needle point directly at the geographic North Pole. If you're standing on the agonic line, your compass will indicate true north without any need for adjustment. Currently, the agonic line runs roughly through parts of North and South America, including portions of the eastern United States. However, because the Earth's magnetic field is constantly changing, the position of the agonic line shifts over time. A location that has zero declination today may have a measurable declination in the future.