What is the largest desert on Earth?
Most people say the Sahara. But a desert is defined by how little precipitation falls, not by sand or heat. By that measure, the largest desert on Earth is covered in ice: Antarctica.
The world's largest deserts, by area
*The Arctic's size depends on where you draw its edge. This common figure treats the whole dry Arctic region as one desert; a narrow ecological definition covers only about 62,000 sq mi (161,000 km²). Either way, Antarctica stays in first place.
"Largest desert" has two answers because "desert" has two meanings. Picture a desert (sand, heat, camels) and the answer is the Sahara. Define a desert the way geographers usually do, by how little water falls from the sky, and the answer is Antarctica. Neither ranking is wrong; they measure different things.
The same trap shows up whenever someone names "the largest," "the most," or "the first." Before arguing about the answer, check what the word in the question was taken to mean.
When someone says "the largest," what did they have to define first?
See the numbers for each desert
| Desert | Type | Area | Typical yearly precipitation |
|---|---|---|---|
| Antarctica | Polar | 5.5M sq mi (14.2M km²) | About 6 in (150 mm) on average; under 2 in (50 mm) inland |
| Arctic* | Polar | 5.4M sq mi (13.9M km²) | Often under 10 in (250 mm); wetter near some coasts |
| Sahara | Hot | 3.6M sq mi (9.2M km²) | Under 0.04 in (1 mm) in the core to 10 in (250 mm) at the edges |
| Arabian | Hot | 900,000 sq mi (2.33M km²) | Mostly under 4 in (100 mm) |
| Gobi | Cold-winter | 500,000 sq mi (1.3M km²) | About 2–8 in (50–200 mm) |
| Kalahari | Hot | 350,000 sq mi (900,000 km²) | About 4–20 in (110–500 mm); much of it semi-arid |
| Patagonian | Cold-winter | 260,000 sq mi (673,000 km²) | About 6–8 in (160–200 mm) |
A desert is a rainfall number, not a look
The usual rule is under about 10 inches (250 mm) a year. The U.S. Geological Survey and National Geographic both describe deserts this way. Snow counts too, measured as the water it melts into. Nothing in the rule mentions sand or temperature.
Antarctica easily qualifies. The whole continent averages about 6 inches (150 mm) of water a year, and its high interior gets under 2 inches (50 mm), less than much of the Sahara's edge. So why is it buried in ice? Because it is so cold that almost nothing melts. Tiny amounts of snow have piled up for hundreds of thousands of years into an ice sheet that averages at least a mile (1.6 km) thick.
The Sahara still earns its reputation. It is by far the largest hot desert, and its core is among the driest places on Earth, with some spots averaging under 0.04 inches (1 mm) of rain a year. It just isn't the biggest desert once cold ones count.
Even the rainfall rule is a simplification. More technical classifications also weigh how much water evaporation could remove, and some of them set the poles aside as their own category because so little evaporates there. The ranking above uses the simple precipitation rule, which is the one behind the popular "Antarctica is the largest desert" claim.
Explore more answers that change with the definition
Definition Switching shows how quietly swapping one meaning of a word for another can flip a conclusion. And Canada vs Mercator Map shows how Canada goes from the 2nd-biggest country to the 4th once you stop counting its lakes and rivers.
Related exhibits
Sources: U.S. Geological Survey, "What Is a Desert?" (arid land receives less than about 10 in / 250 mm of precipitation a year); National Geographic Education, "Desert" (about 10 in / 25 cm or less a year; Antarctica, the Sahara, and the Gobi all qualify); Wikipedia, "Antarctica" (area 5.5M sq mi / 14.2M km²; about 150 mm average precipitation, under 50 mm over the interior; ice sheet averaging at least 1.6 km thick); Wikipedia, "Sahara," "Arabian Desert," "Gobi Desert," "Kalahari Desert," and "Patagonian Desert" (areas and rainfall ranges); Geology.com, "Largest Desert in the World," and Visual Capitalist, "Ranked: The World's Largest Deserts" (Arctic figure of about 5.4M sq mi / 13.9M km²); Wikipedia, "Arctic desert" (narrower ecoregion of 161,400 km²). Precipitation ranges are approximate and vary by location and year.