What is the diameter of the Earth?

Answer: The average diameter of Earth is approximately 12,742 kilometers (7,917.5 miles) because of its oblate spheroid shape.

The Earth’s diameter varies slightly depending on whether we measure it across the equator or between the poles because our planet is not a perfect square, it is an oblate spheroid which means the Earth is slightly flattened at the poles and bulging at the equator. This flattening is due to Earth’s rotational velocity which causes the planet to bulge at the equator. The equatorial diameter representing the widest distance around the Earth is approximately 12,756 kilometers or 7,926 miles. The polar diameter which is the distance from one pole to the other passing through the Earth’s center is slightly smaller. It measures around 12,714 kilometers or 7,900 miles. The difference is about 42 kilometers or 26 miles. The average diameter of the Earth often used as a standard value is obtained by finding the average of equatorial and polar diameters. The average diameter is approximately 12,742 kilometers (7,917.5 miles).