Earth's mean radius

The Earth's mean radius is determined as the average distance from the physical center to the surface, based on a large number of samples. The value, symbolized r_earth, is equal to approximately 6,371,000 meters (6.371 x 10⁶ m). This is roughly 6,371 kilometers (km) or 3,960 statute miles.

The Earth is slightly oblate, so its radius in the plane of the equator is a little larger than its radius along the rotational axis. In addition, there are irregularities in the surface because of hills, mountains, tides, and rainfall.

Based on the value of r_earth given here, the volume of the planet (V_earth), in meters cubed (m³), can be found using the standard formula for the volume V of a sphere in terms of its radius r:

V = (4/3)(pi) r³

where pi represents the ratio of the circumference of a circle to its diameter, an irrational number equal to approximately 3.14159. Based on this formula:

V_earth = 1.083 x 10²¹ m³

Also see Table of Physical Units and Constants.