Magnetic Declination and Bearing Conversion
Magnetic-to-true and true-to-magnetic with east-is-least / west-is-best memo.
Example
You enter
- Declination (deg, +E / -W) 12
- Bearing (deg) 280
- Direction magnetic_to_true
You get
- Result 292.00 deg
Details, formula, and sources
True bearing = magnetic bearing + east declination (or − west declination). 'East is least, west is best' memo. Declination from NOAA NCEI World Magnetic Model.
NOAA NCEI World Magnetic Model (WMM) 2025 by name; U.S. Army FM 3-25.26 by name.
WMM 2025 free at ngdc.noaa.gov/geomag.
Geometry is not forecasting. Avalanche advisory and incident commander govern.
Field names used by the API: declination_deg, bearing_deg, direction, result_deg