Hong Life CalculatorsUnderstanding the antipode calculator — concept and principle
The antipode of a place is the point exactly on the opposite side of the Earth, the other end of a straight line through the centre. This calculator finds the antipode's coordinates in decimal degrees and degrees–minutes–seconds, and gives the distances through and around the Earth.
How it is calculated
- Antipode of (φ, λ) = (−φ, λ ± 180°): the latitude changes sign and the longitude moves halfway round the globe.
- Subtract 180° from an eastern longitude; add 180° to a western one.
- Distance through the centre = 2 × 6,371 km = 12,742 km.
- Distance along the surface = half the circumference = π × 6,371 km ≈ 20,015 km.
The principle
A straight line through the Earth's centre reverses both north–south and east–west position. Latitude is measured from the equator, so the opposite point has the same angle on the other side: north becomes south. Longitude is measured around the axis, so the opposite meridian is 180° away. Because the WGS 84 ellipsoid is symmetric about the centre, the same rule is exact for its latitudes too. At the poles, longitude does not matter: the antipode of the North Pole is the South Pole.
Worked example
Default inputs: Seoul, latitude 37.5665° N, longitude 126.9780° E.
- Antipode latitude = −37.5665°, i.e. 37°33′59″ S.
- Antipode longitude = 126.9780 − 180 = −53.022°, i.e. 53°01′19″ W.
- This point lies in the South Atlantic Ocean, off the coast of Uruguay and southern Brazil.
- Distance through the Earth = 12,742 km; along the surface = 20,015 km.
| Latitude (°, north positive) | Antipode latitude (°) |
|---|---|
| 9.39 | -9.3916 |
| 18.8 | -18.7832 |
| 28.2 | -28.1749 |
| 37.6 | -37.5665 |
| 47 | -46.9581 |
| 56.3 | -56.3498 |
| 75.1 | -75.133 |
How to read the result
Most land has its antipode in the ocean, because about 71% of the Earth's surface is water. Antipodes have opposite seasons (summer in Seoul is winter there) and roughly opposite times of day, about 12 hours apart in solar time.
Common mistakes
- Changing the sign of the longitude instead of adding or subtracting 180°.
- Forgetting to change the latitude's sign.
- Mixing up degrees–minutes–seconds and decimal degrees.
- Using a longitude outside −180° to 180°.
Frequently asked questions
How do I find the antipode of a location?
Change the sign of the latitude and add or subtract 180° from the longitude.
Where is the antipode of Seoul?
In the South Atlantic Ocean at about 37.57° S, 53.02° W, off the coast of Uruguay.
How far away is the antipode?
About 12,742 km through the Earth or about 20,015 km along the surface.
Sources: NASA, Earth Fact Sheet (mean radius 6,371 km) · NGA, World Geodetic System 1984 (WGS 84) definition