The magnetic declination lookup finds the angle between true north and magnetic north at any location. Uses a 10-degree grid approximation of the World Magnetic Model (WMM) 2025–2030 with bilinear interpolation. Essential for accurate compass navigation and surveying.
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Magnetic Declination Results
Compass Correction
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Simplified model, accurate to approximately ±1–2°. For precision navigation use NOAA's official calculator.
Map will appear after lookup
How to Use the Magnetic Declination Lookup
The magnetic declination lookup finds the angle difference between true north (the geographic north pole) and magnetic north (where a compass needle points). This value is essential for converting compass bearings to true bearings used on maps and GPS devices.
Step 1: Enter Your Coordinates
Enter the latitude and longitude in Decimal Degrees. Click "Use My Location" to auto-fill from your browser's GPS. If you don't know your coordinates, look them up with the Latitude/Longitude Finder tool.
Step 2: Click Look Up Declination
Results appear instantly: the declination in degrees East or West, the annual change rate, and a plain-English compass correction instruction. The Leaflet map shows a pin at your location with the declination value in a popup.
How to Correct a Compass Reading
To convert a magnetic compass bearing to a true bearing: East declination, subtract from compass reading. West declination, add to compass reading. The mnemonic "East is least, West is best" helps remember this. Example: you're in New York (declination ~12° West). Your compass reads 30° (NNE magnetic). True bearing = 30° + 12° = 42° (NE true).
Why Declination Changes Over Time
Earth's magnetic field is generated by fluid motion in the molten outer core. This fluid movement causes the magnetic north pole to drift over time — currently moving northward at about 40 km per year toward Siberia. As a result, magnetic declination changes slowly at any given location, typically by 0.1 to 0.2 degrees per year. The World Magnetic Model (WMM) is updated every 5 years to track these changes. The current WMM2025 model is valid through 2030.
Regional Declination Patterns
In the contiguous United States, declination ranges from about 20° West in the Pacific Northwest to 20° East in northern Maine. There is an "agonic line" running roughly from the Great Lakes south through the Mississippi Valley where declination is near zero — no correction needed there. In Western Europe, declination is currently 2–5° West. In Australia, it ranges from 5° West (east coast) to 5° East (west coast).
FAQ
Is this magnetic declination tool free?
Yes, completely free. No signup, no account. Enter any coordinates and get the magnetic declination instantly.
Is my location data safe?
All calculations run locally in your browser using an embedded grid model. No coordinates are sent to any server.
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 — currently about 13° West in New York City, 0° near eastern Michigan, and 20° East in parts of Alaska. When navigating with a compass, you must add or subtract the local declination to get a true bearing.
How do I use magnetic declination to correct my compass?
If declination is West (negative), add the absolute value to your compass reading to get true bearing. Example: compass reads 45° with 12° West declination → true bearing = 57°. If declination is East (positive), subtract it. A mnemonic: 'East is least, West is best' — east declination, subtract from compass; west declination, add to compass.
How accurate is this declination model?
The tool uses a 10-degree grid approximation of the World Magnetic Model (WMM) 2025-2030. Accuracy is approximately ±1-2 degrees for most locations. For precision navigation (surveying, aviation), use NOAA's official WMM calculator at ngdc.noaa.gov.
Does magnetic declination change over time?
Yes. Earth's magnetic field moves slowly, causing declination to change by about 0.1 degrees per year in most regions. The WMM model is updated every 5 years. The current model (WMM2025) is valid through 2030. This tool shows the approximate 2026 value.
What is the difference between magnetic north and true north?
True north is the direction toward Earth's geographic north pole — the axis around which Earth rotates. Magnetic north is where a compass needle points, which is currently located in the Canadian Arctic at about 80.7°N, 108.2°W. The difference between them at any location is the magnetic declination.