ItIt extends from the Arctic in the north to Antarctica in the south, bounded by Asia and Australia in the west and the Americas in the east. At 169.2 million square kilometres (65.3 million square miles) in area, this largest division of the World Ocean - and, in turn, the hydrosphere - covers about 46% of the Earth's water surface and about 32% of its total surface area, making it larger than all of the Earth's land area combined. The equator subdivides it into the North Pacific Ocean and South Pacific Ocean. The Mariana Trench in the western North Pacific is the deepest point in the Pacific and in the world, reaching a depth of 10,911 metres (35,798 ft).

Water temperatures in the Pacific vary from freezing in the poleward areas to about 30 °C (86 °F) near the equator. Salinity also varies latitudinally. The water near the equator is less salty than that found in the mid-latitudes because of abundant equatorial precipitation throughout the year. Poleward of the temperate latitudes salinity is also low, because little evaporation of seawater takes place in these frigid areas.