1.4 × 10¹⁸ t3.09 × 10²¹ lb
All the water in Earth’s oceans weighs about 1.4 × 10²¹ kg, or 1.4 billion billion tonnes (about 3 × 10²¹ lb). No one can weigh it, so it is calculated: NOAA’s ocean volume, 1.335 billion cubic kilometres, times the density of seawater, about 1,025 kg per cubic metre. That is roughly 0.02% of Earth’s mass.
| All the oceans1.335 billion km³, rounded to 1.4 × 10²¹ kg | 1.37 × 10¹⁸ t3.02 × 10²¹ lb |
|---|---|
| Pacific Ocean670 million km³, half of all ocean water | 6.87 × 10¹⁷ t1.51 × 10²¹ lb |
| Atlantic Ocean310 million km³ | 3.18 × 10¹⁷ t7.01 × 10²⁰ lb |
| Indian Ocean264 million km³ | 2.71 × 10¹⁷ t5.97 × 10²⁰ lb |
| Southern Ocean71.8 million km³ | 7.36 × 10¹⁶ t1.62 × 10²⁰ lb |
| Arctic Ocean18.75 million km³, average depth 1,205 m | 1.92 × 10¹⁶ t4.23 × 10¹⁹ lb |
The ocean’s weight is worked out from its volume. NOAA puts the water in the ocean at 1,335,000,000 cubic kilometres (321 million cubic miles); the US Geological Survey gives a very similar 1,338,000,000 km³. Each cubic kilometre is a billion cubic metres.
Seawater is slightly heavier than fresh water because of the salt dissolved in it. At the surface a cubic metre weighs 1,020 to 1,029 kg, depending on temperature and saltiness, and deep down, squeezed by the pressure, it can reach 1,050 kg. Multiplying the volume by a typical 1,025 kg per cubic metre gives 1.37 × 10²¹ kg, which we round to 1.4 × 10²¹.
NASA’s Earth fact sheet arrives at the same place from another direction. It gives the mass of the whole hydrosphere, every drop of water on the planet including ice and groundwater, as 1.4 × 10²¹ kg. About 97% of that water is in the ocean.
Earth itself weighs about 5.97 × 10²⁴ kg, so the oceans are only about 0.023% of the planet’s mass, roughly one part in 4,400. They cover more than 70% of the surface, but at an average depth of just 3,682 m (12,080 ft). The deepest point, Challenger Deep in the Mariana Trench, is about 10,935 m down.
The US Geological Survey pictures it another way: if all of Earth’s water, oceans included, were gathered into one ball, it would be only about 1,385 km (860 miles) across.
The average salinity of seawater is about 35 parts per thousand, so about 3.5% of its weight is dissolved salts. Applied to the whole ocean, that is roughly 4.8 × 10¹⁹ kg of salt, or 48 million billion tonnes. Chloride and sodium make up about 85% of the dissolved ions.
About 3 × 10²¹ lb, or 3 billion trillion pounds. In metric terms it is about 1.4 × 10²¹ kg.
About 1.335 billion cubic kilometres (321 million cubic miles), according to NOAA. That is about 97% of all the water on Earth.
About 1.025 kg at the surface, a little more than a litre of fresh water. A cubic metre weighs about 1,025 kg, ranging from 1,020 to 1,029 kg depending on temperature and salinity.
Seawater is about 3.5% salt by weight, so the whole ocean holds roughly 4.8 × 10¹⁹ kg (48 million billion tonnes) of dissolved salts.
About 3,682 m (12,080 ft), according to NOAA. The deepest point, Challenger Deep, is about 10,935 m (35,876 ft) down.
Last checked October 4, 2026.
