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What Percent of Earth is Water?

What Percent of Earth is Water

Earth - Western Hemisphere

You’ve heard the saying that the Earth is mostly water. But what percent of Earth is water? Salt water oceans make up 71% of the Earth’s surface, which the other 29% made up of the Earth’s continents and islands. But there are also freshwater lakes and glaciers that cover the Earth’s surface.

Of all the water on Earth, 97.5% is contained within the oceans, while the remaining 2.5% is freshwater lakes and frozen water locked up in glaciers and the polar ice caps – almost 69% of the fresh water on Earth is ice. If you could melt all the water on Earth, and the Earth’s surface was perfectly smooth, the water would rise to an altitude of 2.7 km.

But what percent of the Earth is water? Not just the surface of the Earth, but the actual mass of the Earth? Scientists calculate that the mass of the oceans on Earth is 1.35 x 1018 metric tonnes, which is 1/4400 the total mass of the Earth. In other words, the oceans are 0.02% of the total mass of the Earth.

We’ve written many articles about the oceans for Universe Today. Here’s an article about how many oceans there are, and here’s an article about why the ocean is salty.

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.


Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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