What is the diameter of the Earth?

About 8000 miles.

The diameter of the earth at the equator is 12,756.32 kilometers or 7,926.41 miles.

But the diameter of the earth through the poles is 12,715.43 kilometers or 7,901.00 miles.

Thus the earth is 59 km or 25 miles wider than it is tall, giving it a slight bulge at the equator.

This shape is known as an ellipsoid or more properly, geoid (earth-like), or oblate spheroid (squashed sphere). Very Far.