How long is the distance of mantle in the core?

The Earth's mantle extends to a depth of about 2,900 kilometers (1,800 miles) below the surface, while the outer core begins at that depth and extends to about 5,150 kilometers (3,200 miles). Therefore, the mantle does not directly extend into the core; instead, it transitions into the outer core at the mantle-core boundary. The mantle itself is approximately 2,900 kilometers thick.