Largest Desert in the World? It's Not the Sahara

Picture a desert and you probably see sand, heat, and camels. The Sahara, maybe. Spoiler: the largest desert in the world isn't in Africa. It's freezing cold, and you'd never call it a desert by looking at it. Antarctica covers around 14.2 million km² (5.5 million sq mi), making it roughly 1.5 times the size of the Sahara. In this post, we'll show you why, what actually counts as a desert, and how the real top 5 stacks up.

What actually counts as a desert?

A desert isn't what you think. Heat and sand aren't part of the definition. A region counts as a desert if it gets less than 250 millimeters (about 10 inches) of precipitation per year. That's the technical bar.

So you get two flavors. Hot deserts like the Sahara or the Atacama. And cold deserts like Antarctica or the Arctic. No sand required. No heat required.

Once you accept that definition, the rankings of the world's largest deserts flip upside down.

Antarctica is the largest desert in the world

Antarctica covers around 14.2 million km² (5.5 million sq mi). That's roughly 1.5 times the size of the Sahara and nearly twice the size of Australia. On a Mercator map, it looks even bigger, but that's the projection distorting the poles. The real surface area still puts Antarctica on top.

Why does Antarctica count as a desert? In the interior, less than 50 mm of precipitation falls per year on average. The coasts get more, but the continent-wide average sits far below the 250 mm threshold. National Geographic and other sources officially call it the largest desert on Earth.

The McMurdo Dry Valleys, a region in Antarctica, are considered the driest place on Earth. Parts of those valleys are believed to have seen no significant rain or snowfall for around 2 million years. NASA and researchers use the area as a Mars-analog test site.

Plot twist:

The largest desert in the world is freezing cold. Antarctica qualifies as a desert because less water falls from the sky there than in many classic sand deserts.

How much precipitation does Antarctica actually get?

Antarctica averages about 50 millimeters (2 inches) of precipitation per year, with the interior often getting less than 10 mm. For context: New York City gets around 1,200 mm a year. The Sahara averages roughly 100 mm. That makes Antarctica drier per square meter than any classic sand desert on the planet.

The real top 5 deserts by size

Ranked by surface area:

Antarctica at around 14.2 million km² (5.5 million sq mi). Cold desert. Nearly twice the size of Australia.
Arctic at around 13.7 million km² (5.3 million sq mi). Cold desert. Stretches over Greenland, Canada, Russia, Norway, and Alaska.
Sahara at around 9.2 million km² (3.6 million sq mi). Hot desert. About the size of the contiguous United States.
Arabian Desert at around 2.3 million km² (0.9 million sq mi). Hot desert. Covers most of Saudi Arabia, Yemen, Oman, and the UAE.
Gobi at around 1.3 million km² (0.5 million sq mi). Cold desert. Sits between Mongolia and China, can drop below -40 °C in winter.

Two polar deserts at the top. The first sand desert only appears at number 3. Most people only know the hot ones because that's what movies, books, and travel docs show. Polar deserts don't have a PR team.

How cold is the Antarctic desert?

Antarctica isn't just the world's largest desert, it's also the coldest. The average winter temperature in the interior sits around -60 °C (-76 °F). The coldest temperature ever directly recorded on Earth came from Antarctica too: -89.2 °C (-128.6 °F) at Russia's Vostok Station on July 21, 1983.

Water can barely exist at those temperatures, let alone fall from the sky. Whatever moisture does show up arrives as fine, dry snow. Over thousands of years, that built up an ice sheet over 4 kilometers thick in places. Antarctica still counts as arid, because almost nothing comes down per year.

Why the Sahara still matters

The Sahara, at around 9.2 million km² (3.6 million sq mi), is still the largest hot desert in the world and the third-largest desert overall, behind Antarctica and the Arctic. About 11,000 to 5,000 years ago, it wasn't dry at all. It was green. There were lakes, forests, and hippos. Archaeologists have found cave paintings of giraffes and crocodiles. The so-called “Green Sahara” ended when a slight shift in Earth's tilt moved the monsoon belt further south.

The Sahara is still growing today. A 2018 University of Maryland study found that the Sahara has expanded by roughly 10 percent since 1920, mostly southward. About two-thirds of that expansion is linked to natural climate cycles, with the remaining third tied to human-driven effects like climate change and overgrazing.

Test your geography knowledge

Want to see if you can spot other geography myths? We have over 80 geography estimation questions ready to click through. How tall is the tallest mountain really? Which country has the most islands? Free, runs in your browser, perfect for a road trip.

Take-away

The largest desert in the world isn't hot and has no sand. It's Antarctica. A desert is just a very dry region, hot or cold. Next time you hear “desert,” picture ice before sand.

If you like geography plot twists like this, check our posts on how deep the ocean really is or the capital city trap. Or jump straight into the geography quiz.

Which is the largest desert in the world?▾

Antarctica is the largest desert in the world, covering around 14.2 million square kilometers (5.5 million sq mi). It qualifies as a cold desert because it gets less than 250 mm of precipitation per year, the technical threshold for any desert. That makes it roughly 1.5 times the size of the Sahara.

Why does Antarctica count as a desert?▾

A desert is defined by precipitation, not temperature. Antarctica receives only about 50 mm of precipitation per year on average, with the interior often getting less than 10 mm. That puts it well below the 250 mm threshold that classifies a region as a desert.

How much precipitation does Antarctica get?▾

Antarctica gets around 50 millimeters of precipitation per year on average. The interior often receives less than 10 mm, while the coast gets more. For context, New York City averages roughly 1,200 mm of annual precipitation.

How big is the Sahara really?▾

The Sahara covers about 9.2 million km² (3.6 million sq mi). It's the largest hot desert in the world and roughly the size of the contiguous United States. But it's only about two-thirds the size of Antarctica and the third-largest desert overall.

Are there other cold deserts besides Antarctica?▾

Yes. The Arctic is the second-largest desert on Earth at around 13.7 million km². The Gobi Desert in Mongolia and China also qualifies as a cold desert, with winter temperatures that can drop below -40 °C.

What is the coldest temperature ever recorded on Earth?▾

The coldest temperature ever directly recorded on Earth is -89.2 °C (-128.6 °F). It was measured on July 21, 1983, at Russia's Vostok Station in Antarctica. Satellites have later detected even lower surface temperatures in parts of Antarctica.

When was the Sahara green?▾

The Sahara was much wetter and greener between roughly 11,000 and 5,000 years ago. This period is called the “Green Sahara” or “African Humid Period.” It ended when a slight shift in Earth's tilt moved the monsoon belt further south.

Which Is the Largest Desert in the World? Plot Twist