What is magnetic declination?

Magnetic declination is the angle between magnetic north (where a compass needle points) and true geographic north. It varies by location and changes slowly over time as the Earth's magnetic field shifts.

Is east declination positive or negative?

East declination is positive by convention. If your location has a declination of +10° East, magnetic north is 10° east of true north, so you add 10° to your compass bearing to get a true bearing.

How accurate is this estimate?

This tool uses a simplified dipole model and a city lookup table. For precise navigation requiring accuracy better than ±1–2°, use the official NOAA World Magnetic Model (WMM) or the BGS geomagnetic calculator, which incorporate the full spherical harmonic expansion updated every 5 years.

How fast does magnetic declination change?

Declination changes at roughly 0.1°–0.5° per year depending on location, with some high-latitude areas changing faster. Maps and instruments should be updated every 5–10 years; the WMM is refreshed every 5 years.

What is the difference between declination and dip (inclination)?

Declination is the horizontal angle between magnetic north and true north. Dip (or inclination) is the vertical angle — how steeply the field lines plunge into the Earth. Compasses measure declination; dip meters measure inclination.

Why does declination vary so much by location?

The Earth's magnetic pole is not at the geographic pole, and the field is also distorted by variations in the iron-rich rock inside the Earth. Locations near the magnetic pole or large mineral deposits experience larger or more locally variable declination.

Magnetic Declination Calculator

Name: Magnetic Declination Calculator
Availability: InStock
Author: Nham Vu

Enter coordinates or pick a major city to estimate the magnetic declination angle — the difference between true north and magnetic north at that location.

Location Input

Quick pick — major city

or enter coordinates

Latitude (−90 to 90)

Longitude (−180 to 180)

Uses a simplified dipole model — see FAQ for precision notes.

Result

Pick a city or enter coordinates, then click Calculate.

Summary

Enter coordinates or pick a major city to estimate the magnetic declination angle — the difference between true north and magnetic north at that location.

How it works

Select a major city from the dropdown or enter latitude and longitude manually.
The calculator estimates declination using a simplified dipole model based on the World Magnetic Model reference point (geographic north pole vs. magnetic pole offset).
Positive (East) declination means magnetic north lies east of true north — add to compass bearing to get true bearing.
Negative (West) declination means magnetic north lies west of true north — subtract from compass bearing to get true bearing.
Review the compass correction formula shown for your location and apply it to navigation tasks.

Use cases

Correct compass readings when hiking or orienteering in areas with significant declination.
Calibrate survey instruments that reference magnetic north before converting to true north bearings.
Teach students the concept of magnetic declination and its geographic variation.
Plan flight routes that require conversion between magnetic and true headings.
Adjust hunting or backcountry navigation with a baseplate compass and a paper topo map.
Cross-check GPS true-north readings against magnetic-north compass readings.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu