In geography, the antipode of any spot on Earth is the point on Earth's surface diametrically opposite to it.
To calculate the antipode, enter the latitude and longitude in decimal degrees format. This format may begin with a negative sign ( - ) to indicate direction East of the Prime Meridian (longitude 0°) at Greenwich, England.
The latitude simple changes from a positive value North of the Equator to a negative value South of the Equator or vice versa. So there's no real need to calculate it.
Latitude: 37.7749 (for San Francisco, California, USA)
Longitude: -122.4194 (for San Francisco, California, USA)
The antipode is:
Latitude: -37.7749
Longitude: 57.580600
Download the free Google Earth Pro to view locations by Latitude and Longitude: https://earth.google.com/web/