The distance to the center of the Earth is approximately 6,371 kilometers (3,959 miles) on average. This value varies slightly because the Earth is not a perfect sphere but an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator. The distance from the center of the Earth to the equator is about 6,378 kilometers (3,963 miles), while from the center to the poles, it is about 6,357 kilometers (3,949 miles).