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

Without declination correction, your compass bearings will be off by the declination angle. For example, if the declination is 12° East and you follow an uncorrected compass bearing of 0° (north), you'll actually be heading 12° east of true north. Over a distance of 1 mile, this error could put you roughly 1,100 feet off course. For hikers, pilots, sailors, surveyors, and military personnel, accurate declination correction is essential for safe and precise navigation.

This estimator uses the World Magnetic Model 2020 (WMM2020), the same standard model used by NOAA, NATO, and the U.S. Department of Defense. It computes the Earth's magnetic field using spherical harmonic coefficients up to degree 12, accounting for the main geomagnetic field and its secular variation. The model is valid from 2020 through 2025 and provides accuracy typically within ±0.5° for most populated regions.

Declination is the horizontal angle between true north and magnetic north (measured in the horizontal plane). Inclination (or magnetic dip) is the vertical angle that the magnetic field makes with the horizontal plane—it ranges from -90° at the South Magnetic Pole to +90° at the North Magnetic Pole. At the magnetic equator, inclination is approximately 0°, meaning the field is horizontal. Both values are important for different applications: declination for compass navigation, inclination for geological surveys and some advanced navigation systems.

Magnetic declination changes continuously due to the dynamic nature of Earth's liquid outer core. The annual change (secular variation) typically ranges from a few arc-minutes to over 10 arc-minutes per year, depending on location. In some regions near the magnetic poles, changes can be even more dramatic. The WMM model is updated every 5 years (2020, 2025, etc.) to account for these shifts. For critical navigation, always use the most current declination data. This tool automatically adjusts for the date you input using the model's secular variation coefficients.

No—magnetic declination varies significantly across the globe. Near the magnetic poles, declination can swing wildly. For example:

• New York City: ~12° West
• London: ~1° East (near-zero line passes through the UK)
• Tokyo: ~7° West
• Cape Town: ~24° West
• Northern Canada: Can exceed 40° East

There's even an agonic line (where declination = 0°) that currently runs roughly through the central United States and eastern Europe—along this line, a compass points directly to true north.

Yes! Modern smartphones can provide GPS coordinates, which this tool uses to calculate declination. Simply click the "GPS Locate" button, and your device will provide its current latitude and longitude (with your permission). However, GPS itself gives true bearings, not magnetic ones. So if you're using a physical magnetic compass alongside GPS, you still need to apply the declination correction. Many hiking and navigation apps automatically handle this conversion, but it's wise to understand the underlying principle.

This tool is valuable for:

• Hiking & Backpacking: Correctly orienting topographic maps with a compass
• Sailing & Boating: Converting between true and magnetic bearings for navigation
• Aviation: Runway numbering and VOR navigation rely on magnetic bearings
• Surveying: Precise land measurements require true north references
• Amateur Radio: Orienting directional antennas for long-distance communication
• Astronomy: Aligning telescopes with true celestial poles
• Education: Teaching earth science and geomagnetism concepts