The mantle itself is about 2,900 kilometers (1,800 miles) thick. The upper mantle, which is the portion directly below the crust, is about 660 kilometers (410 miles) thick.
Therefore, the lower mantle, which is often considered synonymous with the "inner mantle" in some contexts, would be approximately 2,240 kilometers (1,390 miles) thick.
It's important to note that these are estimates, and the actual thickness can vary slightly depending on the location and methodology used for measurement.
