Magnetic Variation Calculator

Formula

To calculate the Magnetic Variation (MV):

$$MV = D + (M \times Y)$$

Where:

MV is the magnetic variation (degrees)
D is the declination at the start of the year (degrees)
M is the annual change in declination (degrees per year)
Y is the number of years since the start of the year

What is Magnetic Variation?

Magnetic variation, also known as magnetic declination, is the angle between magnetic north and true north at a particular location. It is the result of the Earth's complex and ever-changing magnetic field. This variation is important to consider in navigation and compass-based activities, as it can cause a significant difference between the compass bearing and the actual geographic direction. The value of magnetic variation changes depending on where you are on the Earth and also changes slowly over time.

Example Calculation 1

Let's assume the following values:

Declination at the Start of the Year (D) = 5 degrees
Annual Change in Declination (M) = 0.1 degrees per year
Number of Years Since the Start of the Year (Y) = 10

Using the formula:

$$MV = 5 + (0.1 \times 10) = 5 + 1 = 6$$

The Magnetic Variation is 6 degrees.

Example Calculation 2

Let's assume the following values:

Declination at the Start of the Year (D) = 2 degrees
Annual Change in Declination (M) = 0.2 degrees per year
Number of Years Since the Start of the Year (Y) = 15

Using the formula:

$$MV = 2 + (0.2 \times 15) = 2 + 3 = 5$$

The Magnetic Variation is 5 degrees.