Use this cartographic calculation to convert, scale, or compare map, terrain, bearing, raster, or route quantities when the coordinate and unit conventions are explicitly known.

Initial Declination Degrees (deg)

Required number input.

Annual Change Degrees Per Year (deg/year)

Required number input.

Elapsed Years (year)

Required number input.

Project signed east-positive magnetic declination using a signed annual change in degrees per year. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Projected Declination Degrees (deg)

The resulting projected declination degrees returned as a number.

• Map calculations depend on datum, projection, latitude, scale definition, magnetic-declination epoch, and whether distances are planar, rhumb-line, or geodesic. A compact formula cannot remove distortion or infer the missing reference system.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Confirm the map datum, projection, scale, and bearing convention before applying the result. Use geodesic or GIS software with current reference data when survey-grade or navigation-critical accuracy is required.

• Grid To Magnetic Converter

  Magnetic azimuth from grid azimuth, signed grid convergence (true minus grid), and east-positive declination.

• Magnetic Declination Applier

  True azimuth from magnetic azimuth plus signed east-positive magnetic declination.

• Magnetic To Grid Converter

  Grid azimuth from magnetic azimuth, signed grid convergence (true minus grid), and east-positive declination.