The equatorial radius of the Earth is approximately 6,378 kilometers (3,963 miles). This measurement represents the distance from the Earth's center to its equator. It's worth noting that the Earth is not a perfect sphere but rather an oblate spheroid, meaning it is slightly flattened at the poles and bulges at the equator due to its rotation. As a result, the polar radius (from the Earth's center to the North or South Pole) is slightly shorter, around 6,357 kilometers (3,949 miles).