It’s about 6km deep if you’re at the equator, and about 4km deep if you’re at the North pole. This is because Earth is not a perfect sphere, it’s radius is bigger at the equator than at the poles. The proper name for the shape of Earth is “oblate spheroid” !!
The Earth actually has two cores, an inner and an outer core. We know this due to tracking the movement of earthquakes as they pass through the Earth. The distance from Earth’s surface to its center is about 3,975 miles (6,395 kilometers). Scientists have divided the interior of Earth into various layers, based on their composition. The crust, or outer portion, varies in depth from 5 to 25 miles (8 to 40 kilometers). Below the crust is the mantle, which extends to a depth of about 1,800 miles (2,900 kilometers). Below that is the core, composed of a liquid outer core about 1,380 miles (2,200 kilometers) in depth, and a solid inner core about 780 miles (1,300 kilometers) deep.
The inner core of the Earth, its innermost hottest part as detected by seismological studies, is a primarily solid ball about 1,220 km (760 mi) in radius, or about 70% that of the Moon. It is believed to consist of an iron–nickel alloy, and may have a temperature similar to the Sun’s surface, approximately 5700 K (5430 °C).
The outer core of the Earth is a liquid layer about 2,266 km (1,408 mi) kilometers thick composed of iron and nickel which lies above the Earth’s solid inner core and below its mantle. Its outer boundary lies 2,890 km (1,800 mi) beneath the Earth’s surface. The transition between the inner core and outer core is located approximately 5,150 km (3,200 mi) beneath the Earth’s surface.