The shape of the Earth is an oblate spheroid, which means it is roughly spherical in shape but slightly flattened at the poles and bulging at the equator. This shape is due to the Earth’s rotation and the centrifugal force it creates, which causes the equatorial region to be slightly wider than the polar regions. The Earth’s equatorial diameter is about 43 kilometers (27 miles) larger than its polar diameter, and its average diameter is approximately 12,742 kilometers (7,917 miles).