Approximately how thick is the mantle?

The mantle is the majority-solid core of the interior of the Earth. The mantle lies between the dense, super-heated core of Earth, and the crust, its thin outer layer. The mantle is about 2,900 kilometers (1,802 miles) thick and comprises a whopping 84 per cent of the total volume of Earth.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and neptune