section_path: Physical characteristics/Size and shape
section_name: Size and shape
paragraph_text: Size and shape
  
  Earth has a rounded shape, through hydrostatic equilibrium, with an average diameter of 12,742 kilometres (7,918 mi), making it the fifth largest planetary sized and largest terrestrial object of the Solar System.
  
  Due to Earth's rotation it has the shape of an ellipsoid, bulging at its Equator; its diameter is 43 kilometres (27 mi) longer there than at its poles. Earth's shape furthermore has local topographic variations. Though the largest local variations, like the Mariana Trench (10,925 metres or 35,843 feet below local sea level), only shortens Earth's average radius by 0.17% and Mount Everest (8,848 metres or 29,029 feet above local sea level) lengthens it by only 0.14%. Since Earth's surface is farthest out from Earth's center of mass at its equatorial bulge, the summit of the volcano Chimborazo in Ecuador (6,384.4 km or 3,967.1 mi) is its farthest point out. Parallel to the rigid land topography the Ocean exhibits a more dynamic topography.
  
  To measure the local variation of Earth's topography, geodesy employs an idealized Earth producing a shape called a geoid. Such a geoid shape is gained if the ocean is idealized, covering Earth completely and without any perturbations such as tides and winds. The result is a smooth but gravitational irregular geoid surface, providing a mean sea level (MSL) as a reference level for topographic measurements.