The depth of the Earth is typically measured from its surface to its center. The radius of the Earth is approximately 3,959 miles (6,371 kilometers), which means the distance from the surface to the center is roughly half that value, or about 1,979.5 miles (3,185 kilometers). However, it's important to note that the Earth is not a perfect sphere; it bulges slightly at the equator and is flatter at the poles. The depths provided here are rough estimates based on average measurements.