The southern hemisphere starts at 0 and ends at south pole. what's the measurement
of the south pole?

The South Pole is 90 degrees South.

Explanation:

This measurement is a line of latitude. The Earth is a sphere. As such, it is divided up like protractor. If you could simply walk straight through the Earth It would be a straight line. The North pole is 90 degrees North and the South is 90 degrees South. We use these measurements to indicate directions are crucial to help us navigate and explain what happens on Earth.