How tall is Mount Everest?

How tall is Mount Everest?

Mount Everest's summit stands 8,848.86 m (29,031.7 ft) above sea level, the figure used on this site. It is the result of a joint survey by Nepal and China, announced on 8 December 2020, and it is now the internationally accepted height of the world's highest mountain. Everest straddles the border between Nepal and the Tibet Autonomous Region of China, in the Mahalangur Himal section of the Himalaya. In Nepali it is called Sagarmatha, and in Tibetan Chomolungma (Qomolangma).

To put 8,848.86 m in perspective: it is more than ten times the height of Burj Khalifa, the tallest building on Earth, and only a few kilometers below the typical cruising altitude of a long-haul airliner. You can try to fit the mountain alongside buildings and people in the 3D height comparison tool, though at this scale a human figure becomes a speck.

A century and a half of measuring Everest

Everest's height has been revised many times, and each new figure reflects improvements in technology as much as any change in the mountain.

The original survey: Peak XV

In the mid-19th century the Great Trigonometrical Survey of India, a decades-long British project led successively by George Everest and Andrew Waugh, was mapping the subcontinent by triangulation. Observers measured angles to distant Himalayan peaks from stations on the plains more than 150 km away. In 1852, the mathematician Radhanath Sikdar, working from those observations, concluded that the summit labeled Peak XV was the highest yet recorded.

Waugh announced the result in 1856: 29,002 ft. The calculation had actually come out at exactly 29,000 ft, but the extra 2 ft were reportedly added so the figure would not look like a rough estimate. Waugh proposed naming the peak after his predecessor, George Everest, and the Royal Geographical Society adopted the name in 1865, despite Everest's own reservations.

Why the numbers kept changing

The early figures were remarkably close to modern values given that surveyors never came within 150 km of the summit. Variations since then come from four main sources:

• Snow cap versus rock. The summit is capped by snow and ice whose depth changes with season and year. China's 2005 survey used ground-penetrating radar to separate the rock surface (8,844.43 m) from about 3.5 m of overlying snow and ice.
• Defining sea level. Heights are measured relative to the geoid, a model of mean sea level extended under the continents. Under the Himalaya, the mass of the mountains distorts gravity and therefore the geoid, and uncertainties in that model were a major source of disagreement before 2020.
• Refraction. Light bends as it passes through layers of air of different density, which affected theodolite measurements from far away.
• Tectonics and earthquakes. The mountain is still being pushed up, by roughly 4 mm a year by some estimates, by the collision of the Indian and Eurasian plates, and large earthquakes, such as the one that struck Nepal in April 2015, can shift the ground by centimeters.

The 2020 joint survey

Nepal planned its own survey in 2019, partly to find out whether the April 2015 earthquake had changed the mountain's height, and China carried out a new survey in spring 2020, a season when foreign expeditions were barred because of the COVID-19 pandemic. Both relied on satellite positioning from the summit combined with improved gravity data for the geoid. The two countries reconciled their data and announced the common figure of 8,848.86 m, ending a decade in which Nepal used 8,848 m and China 8,844.43 m. The new value is 86 cm higher than the old Survey of India figure, a difference that reflects better methods rather than measurable growth.

Everest in feet and why the conversions differ

Because American and British readers often think of Everest in feet, it is worth knowing where the commonly quoted numbers come from. One meter equals exactly 3.28084 ft, so the current official height converts as follows:

Older atlases, school textbooks and souvenir signs may therefore show any of four or five different numbers, all of them legitimate for their time. When you see 29,029 ft, the source predates December 2020. When you see 29,035 ft, it is usually based on the 1999 American GPS work. Only 29,032 ft (or 29,031.7 ft) reflects the current joint measurement used on this site.

Because the difference between the old and new figures is less than a meter, none of these revisions changes Everest's rank. Its nearest rival, K2 on the Pakistan–China border, is about 238 m lower, so Everest's title as the highest point above sea level is secure regardless of which survey you use. You can convert any other summit height with the height converter.

Highest, tallest or farthest from Earth's center?

"Highest mountain" depends on how you measure. NOAA's National Ocean Service puts it neatly: the answer changes with the reference point.

Chimborazo benefits from Earth's equatorial bulge: because the planet is wider at the equator, a summit near 1°S starts much farther from the center. NOAA puts the difference at about 2,072 m, while other calculations give about 2,168 m; both agree Chimborazo wins on this measure.

Base-to-summit comparisons are also less flattering to Everest than its altitude suggests. Because it rises from the high Tibetan Plateau and from valleys already around 4,000 to 5,000 m high, its rise above its immediate base is only about 3,650 to 4,650 m, less than Alaska's Denali, which rises roughly 5,600 m from its surrounding lowlands.

Mount Everest compared with other landmarks

The scale difference between Everest and human-made structures is enormous. This table uses the heights in this site's data.

You could stack almost 27 Eiffel Towers or about 64 Great Pyramids of Giza to reach the summit. Even Burj Khalifa, the tallest structure ever built, would need to be stacked more than ten times. For more comparisons, browse the landmarks hub or see the tallest lists.

Life at 8,849 meters

At the summit, air pressure is about one-third of that at sea level: Wikipedia's figures give roughly 33.7 kPa against 101.3 kPa. The proportion of oxygen in the air is the same as at sea level, but each breath delivers only about a third as many oxygen molecules. Strong winds can lower the effective pressure further. This is why the zone above about 8,000 m is called the "death zone": the human body cannot acclimatize to it and deteriorates the longer it stays.

Most climbers use bottled oxygen above the high camps, although a small number have reached the summit without it. Temperatures at the top can fall below −30 °C even in the spring climbing season, and jet-stream winds make the summit unreachable for much of the year.

Climbing records and statistics

The first confirmed ascent was made on 29 May 1953 by Edmund Hillary of New Zealand and Tenzing Norgay, a Sherpa from Nepal, via the South Col and Southeast Ridge, as part of a British expedition. A Chinese team made the first ascent via the North Ridge in 1960, and Junko Tabei of Japan became the first woman on the summit in 1975.

Statistics on Everest climbs come largely from the Himalayan Database, which grew out of the decades of interviews the journalist Elizabeth Hawley conducted with expeditions in Kathmandu. It now holds more than 11,800 expedition records across the Nepal Himalaya, covering both sides of border peaks such as Everest.

The record permits and summit numbers have brought problems of crowding near the top, where climbers can wait in line on narrow ridges at extreme altitude. Nepal's government has periodically revised its rules on fees, experience requirements and waste to manage the traffic.

How Everest's height affects the world around it

Everest is the centerpiece of a range that shapes weather across Asia. The Himalaya block the monsoon, creating the wet plains of India and the dry plateau of Tibet, and their glaciers feed rivers on which hundreds of millions of people depend. The jet stream often strikes the summit in winter, producing the famous plume of snow blowing from its peak, a visual sign of how high it protrudes into the upper atmosphere.

For a sense of how our own bodies compare, an adult of 175 cm (5′9″) is about 1/5,000th of Everest's height. To see the mountain beside the world's tallest buildings, open the 3D comparison tool.