Magnetic Declination Calculator
Calculate magnetic declination angle between true north and magnetic north at any location worldwide. Free online calculator with charts and field breakdown.
About This Calculator
The Magnetic Declination Calculator helps you find the angular difference between true north (geographic north pole) and magnetic north (where a compass needle points) at any location on Earth. This value is essential for accurate navigation using a compass — without correcting for declination, your bearings can be significantly off, especially at higher latitudes and coastal regions.
This calculator uses a tilted dipole model of Earth's magnetic field, calibrated to the World Magnetic Model 2025 parameters. It accounts for the position of the magnetic north pole (currently near 80.8°N, 107.3°W), elevation above sea level, and secular variation — the slow drift of the magnetic pole over time. The model computes the full magnetic field vector and derives declination, inclination, and total intensity from it.
Regional Notes
India: Magnetic declination in India is generally small (<2°). The zero-declination line passes through central India. Hikers, surveyors, and orienteering enthusiasts should check local declination for precision work, though the small correction is often negligible for casual compass use.
United States: Declination across the US varies dramatically from about 16° west in Maine to 16° east in Washington state. The agonic (zero) line currently runs from the Great Lakes through the Mississippi River valley. The USGS recommends checking declination annually for land surveying and backcountry navigation.
United Kingdom: The UK is close to the agonic line, with declination ranging from 0° to 4° west. This is a significant shift from 1800 when declination was about 24° west. British Ordnance Survey maps include declination information in their legends, and the UK Met Office provides updates through the British Geological Survey.
Frequently Asked Questions
What is magnetic declination?
Magnetic declination is the angle between true north (geographic north pole) and magnetic north (where a compass needle points). It varies by location and changes slowly over time due to shifts in Earth's magnetic field.
Why does magnetic declination matter for navigation?
When using a compass for navigation, you must account for magnetic declination to find true north. Without correcting for declination, your bearings can be off by up to 20 degrees depending on your location, leading to significant navigation errors over distance.
How accurate is this magnetic declination calculator?
This calculator uses a tilted dipole approximation of Earth's magnetic field based on the World Magnetic Model parameters. While not as precise as the full WMM, it provides a reasonable estimate of declination, inclination, and field strength for most locations worldwide.
How does magnetic declination vary in India?
In India, magnetic declination is relatively small. In Mumbai (19°N, 73°E) it is about 0° to 1° west, in Delhi (29°N, 77°E) about 1° to 2° west, and in Chennai (13°N, 80°E) about 1° to 2° east. Eastern India has slightly positive declination while western India has slightly negative declination.
How does magnetic declination vary in the United States?
In the United States, declination varies widely. The East Coast (New York) has about 12° west declination, the Midwest (Chicago) about 5° west, the West Coast (Los Angeles) about 11° east, and the Pacific Northwest (Seattle) about 15° east. The agonic line (zero declination) currently runs through the Mississippi River region.
How does magnetic declination vary in the United Kingdom?
In the United Kingdom, magnetic declination is currently about 0° to 3° west. The agonic line (where declination is zero) passes close to eastern England. In London, declination is approximately 1° west, while in Scotland it can reach 3° to 4° west. The UK has seen declination shift from about 10° west in 1800 to near zero today.
What is magnetic inclination or dip angle?
Magnetic inclination (also called dip angle) is the angle that Earth's magnetic field makes with the horizontal plane. It ranges from 0° at the magnetic equator to 90° at the magnetic poles. In the northern hemisphere, the field points downward (positive inclination), while in the southern hemisphere it points upward (negative inclination).
How often does magnetic declination change?
Magnetic declination changes continuously as Earth's magnetic field evolves. The magnetic north pole is currently moving at about 50-60 km per year toward Russia. The World Magnetic Model is updated every 5 years to account for these changes. For most practical navigation, checking declination within a year or two is sufficient.