Degrees True to Magnetic Calculator

When navigating with a compass, you need to account for magnetic variation to get accurate bearings. This calculator helps you convert true degrees to magnetic degrees by applying the local magnetic declination for your location.

What is True vs Magnetic Degrees?

True degrees (also called geographic degrees) are based on the Earth's geographic coordinate system, where 0° is at the Prime Meridian in Greenwich, England. Magnetic degrees (also called compass degrees) are based on the Earth's magnetic field, which causes compass needles to point north.

The difference between true and magnetic degrees is called magnetic declination or variation. This variation changes over time and varies by location. A positive declination means magnetic north is east of true north, while a negative declination means magnetic north is west of true north.

Magnetic declination is not the same as compass deviation. Deviation is caused by local magnetic fields from metal objects near the compass, while declination is caused by the Earth's magnetic field.

How to Convert True to Magnetic Degrees

To convert true degrees to magnetic degrees, you need to know the magnetic declination for your location. The formula is:

Magnetic Degrees = True Degrees ± Declination

Where the sign depends on whether magnetic north is east or west of true north.

For example, if you're at a location with a declination of 10° east, and you want to navigate true north (0°), you would set your compass to 10° magnetic north.

If you're navigating in the opposite direction, you would subtract the declination. For example, if you want to navigate true south (180°) at the same location, you would set your compass to 170° magnetic north.

Practical Applications

Understanding the difference between true and magnetic degrees is essential for:

Navigation with a compass
Surveying and mapping
Hiking and outdoor activities
Boating and aviation
Military and security operations

Always check the current magnetic declination for your location before using a compass. Declination changes over time due to natural magnetic field variations.

FAQ

How do I find the magnetic declination for my location?

You can find the magnetic declination for your location using online declination calculators, government mapping services, or compass apps that provide this information.

Does magnetic declination change over time?

Yes, magnetic declination changes gradually over time due to natural magnetic field variations. It's important to check the current declination for your location before using a compass.

What is the difference between magnetic declination and compass deviation?

Magnetic declination is caused by the Earth's magnetic field and varies by location. Compass deviation is caused by local magnetic fields from metal objects near the compass and can be corrected by adjusting the compass.