The earth is not a true sphere so it has no single diameter. At the equator the diameter is about 7926 miles whereas it is about 7900 miles at the poles. This is primarily caused by the earths rotation
The Earth is not a perfect sphere, so it has more than one diameter. Pole-to-pole, the diameter is 12,714 kilometers, 12,756 kilometers at the equator. That's an average of 7,917.5 miles.
