Magnetic Declination Calculator
Magnetic declination (or variation) is the angle between true north and magnetic north at your location. A compass needle points to magnetic north, not true north, so you need to know the declination to navigate accurately with a map and compass. East declination means magnetic north is east of true north; west declination means it is west.
This calculator uses a simplified dipole model based on the approximate position of Earth's magnetic north pole (~80.7°N, 72.7°W as of 2025). For mission-critical navigation, use the official World Magnetic Model (WMM) or IGRF data from NOAA, which accounts for the full complexity of Earth's magnetic field.
The declination varies widely across the globe:
- US East Coast: Roughly -10° to -15° (west declination)
- US West Coast: Roughly +12° to +16° (east declination)
- Central US: Near 0° along the agonic line
- UK: Roughly -1° to +2°
- Australia: Roughly +5° to +12° (east)
To convert a compass bearing to a true bearing:
True Bearing = Magnetic Bearing + Declination
Remember: "East is least, west is best." East declination is added, west declination is subtracted (it is already negative in this calculator).
Important: Magnetic declination changes over time as Earth's magnetic poles drift. The north magnetic pole moves roughly 40-50 km per year. Maps printed years ago may show outdated declination values. Always check current declination before a trip.