The diameter of the Earth west to east is the same as its equatorial diameter, which is 12,756 kilometers (7,926 miles).

It's important to distinguish between:

* Equatorial diameter: The distance across the Earth at the equator.

* Polar diameter: The distance across the Earth through the poles.

The Earth is slightly flattened at the poles, meaning the polar diameter is 12,714 kilometers (7,900 miles), which is slightly smaller than the equatorial diameter.