Antipode Calculator

The antipode is the point on Earth's surface that is exactly opposite to where you are standing. Imagine a straight line passing through the center of the earth and going to the other side of the planet. The point at which this line intersects with the Earth's surface is your antipode, and it is also the farthest place from you that you can reach without leaving the ground.

The word comes from the Greek and means "opposite foot". Two people at their antipodes have their soles facing each other with the Earth in between.

What is an antipode?

Every point on Earth has exactly one antipodal point. To find it, reverse two compass directions: north becomes south and east becomes west. Every point in the Northern Hemisphere is necessarily in the Southern Hemisphere, and every point in the Eastern Hemisphere is necessarily in the Western Hemisphere.

The oceans cover more than 70% of the Earth's surface and most of the land mass is in the Northern Hemisphere, so antipodes of random points on land will usually be in open ocean. Only about 4% of land has another piece of land as its antipode. For this reason, a hole dug to reach the other side of the world would usually go into the sea.

This is how to use this calculator.

Enter the latitude and longitude of your starting point. You can enter decimal degrees with signs where north and east are positive while south and west are negative. Alternatively you can use hemisphere mode to enter normal values then select one of the four cardinal directions (N, S, E, W).

The calculator will instantly return a human-readable expression such as "40.71 degrees south latitude, 105.99 degrees east longitude", in addition to the antipodal point's latitude and longitude values. If you open the "Degrees, Minutes, Seconds" option, you can see the same result in the format used by many maps and GPS devices.

Formula:

The calculation of the antipodal point involves a two-step inversion of coordinates. First, the sign of the latitude is inverted. Then, the longitude is adjusted by either adding or subtracting 180 degrees to ensure that it falls within the normal range of -180 to 180.

For example, New York City is located at latitude 40.71 degrees north and longitude 74.01 degrees west. In signed decimal degrees notation, the latitude is 40.71 and the longitude is -74.01. By inverting the sign of the latitude we get -40.71. Since the longitude is negative, we add 180 to it, giving us 105.99. The antipode of New York City is located at 40.71 degrees south latitude and 105.99 degrees east longitude in the Indian Ocean southwest of Australia.

This conversion is accurate. The only source of inaccuracy is the accuracy with which you know your own coordinates. This is because inversion assumes that the earth is a perfect sphere.

Examples of antipodes:

Here are some well known places and their antipodes on the opposite side of the Earth. Most antipodes are in the ocean but there are a few cases where land points are antipodal to each other.

How far is it to my antipode?

Your antipode is the point on Earth that's farthest from you and it doesn't matter where you are. The straight-line distance through the earth to your antipode is equal to the diameter of the earth, which is about 7901 miles (12742 km). The surface-distance along a great circle between you and your antipode is half of the circumference of the earth, or about 12,430 miles (20,015 km).

If one could fall through a frictionless tunnel straight to the antipodes, gravity would take them there in about 42 minutes and they would reach almost 8 km/s at the center of the Earth. Robert Hooke suggested this concept in the 17th century. This value of 42 minutes is true for any straight tunnel through the earth.

Where are antipodes?

Antipodes are not just an interesting curiosity. Seismologists study how earthquake waves concentrate at points exactly opposite the epicenter. Radio engineers point their antennas toward great circle routes that lead to distant communication partners. At maximum range this route runs near the antipode. Long satellite links present the greatest challenge in terms of geometric relationship between ground stations located close to the antipodes.

There is a beautiful mathematical conclusion as well. According to the Borsuk-Ulam theorem, there exists at least one point on Earth where temperature and air pressure are identical at any given time - an antipodal pair.

Tip:

Be careful with the signs. A common mistake is to enter a length west of the Prime Meridian as a positive number, which will put the antipode in the wrong hemisphere. In Hemisphere mode you can select the direction directly and avoid this problem.

If you want to check out a real place, first find the coordinates with a map app and enter them here. If you keep four decimal places, then you can locate it within about 11 meters. That's enough to find a point that is the other side of the world from where you are.