Why Mount Everest is Now 8,848.86m The Story Behind the Number That Changed Everything

On December 8, 2020, Nepal’s Foreign Minister Pradeep Gyawali stood at a lectern in Kathmandu and made an announcement that altered a number that had been in every geography textbook on earth for sixty-six years.

“This is a historic day,” he said.

He was right. For the first time in Nepal’s history as an independent nation, the country had conducted its own measurement of the world’s highest mountain and the number it produced, jointly confirmed with China, was 8,848.86 metres. Not the 8,848 metres that the world had accepted since 1954. Not the 8,844.43 metres that China had insisted on for fifteen years. A new figure, 86 centimetres higher than the old one, produced by better technology, more surveyors, and crucially a political agreement that had taken a decade to reach.

The number is not just a number. It is the endpoint of a 175-year argument about how you measure the highest point on earth, who has the authority to do the measuring, and what exactly you are measuring when you stand at the summit of Everest and take a reading.

This is the story of how 8,848.86 happened.

The Original Measurement: How 8,848 Was Calculated and Why It Survived So Long

The number that defined Everest for sixty-six years was not produced by Nepal. It was not produced by China. It was produced by the Survey of India a British colonial cartographic operation that was, in the mid-nineteenth century, conducting the most ambitious surveying project in human history.

The Great Trigonometrical Survey of India had been working across the subcontinent since 1802. Its task was to map the entire Indian subcontinent with unprecedented precision a project that by the time it reached the Himalayan foothills in the 1840s had already taken four decades and killed many of its surveyors through disease, exhaustion, and the logistical impossibility of what they were attempting.

The precise height of Mount Everest had been contested ever since a group of British surveyors in India declared the height of Peak XV as it was initially called to be 8,778 metres in 1847. That first estimate was wrong by 71 metres. The corrected figure came seven years later.

In 1856, Radhanath Sikdar a Bengali mathematician working for the Survey calculated from multiple theodolite readings taken across the Terai that Peak XV was 29,002 feet (8,839 metres). After corrections for atmospheric refraction, temperature gradients, and the curvature of the earth, the figure was adjusted to 29,028 feet. In 1865, the mountain was renamed Everest, after Sir George Everest, the Surveyor General of India a man who had never been within hundreds of kilometres of the peak that would bear his name.

The official Everest snow height of 8,848 metres (29,028 feet) was measured by the Survey of India in 1954. This is the measurement that went into the textbooks. This is the number that two generations of schoolchildren memorised as definitively as they memorised the boiling point of water.

It survived for sixty-six years for a simple reason: it was good. The Survey of India surveyors, working with nineteenth-century instruments across terrain that still challenges modern equipment, produced a figure that modern GPS technology has revised by less than one metre. The original 8,848 metre measurement was off by 86 centimetres approximately the distance from your elbow to your fingertip.

This is not a story of old science being replaced by new science. It is a story of a number that was nearly right becoming officially precise.

The Snow Cap vs Rock Height Problem: The Dispute That Lasted 66 Years

The reason the mountain’s height remained contested for so long was not primarily a measurement problem. It was a definitional one.

When you stand at the highest point on earth, you are not standing on rock. You are standing on a variable, shifting, accumulating cap of snow and ice that sits on top of the rock. The rock does not move at least, not on human timescales. The snow does. It accumulates during monsoon. It compacts under wind. It melts at the margins. It is replenished every year in different quantities depending on the season’s precipitation. On any given day, the snow cap at Everest’s summit might be anywhere from 50 centimetres to 2 metres thick.

So which do you measure?

Chinese authorities had said previously Mount Everest should be measured to its rock height, while Nepalese authorities argued the snow on top of the summit should be included.

This was not a frivolous argument. It reflected a genuine scientific disagreement about what “height” means for a mountain. The rock height is the height of the Earth’s permanent geology the number that does not change year to year, that is not affected by weather, that represents the mountain’s actual geological elevation. The snow height is the height that climbers actually reach, that flags are actually planted at, that the summit experience actually takes place on.

China had claimed the height to be 8,844.43 metres the rock height while Nepal had claimed 8,848 metres using the top of the snow. And using the best GPS technology available, the US National Geographic Society measured the height of the mountain as 8,850 metres in 1999.

Three countries, three measurements, spanning a range of nearly 6 metres, all measuring the same mountain but answering different versions of the same question.

The 2020 joint survey resolved this by doing something no previous measurement had done completely: measuring both at the same time.

The Joint Survey: What Nepal and China Actually Did

The agreement to jointly announce the new measurement of the Earth’s highest point was made during Chinese President Xi Jinping’s visit to the Nepalese capital, Kathmandu in 2019. The survey itself had begun years earlier.

Nepal had been working on the measurement of Everest since 2011. The motivation was not simply scientific accuracy it was sovereignty. Nepal’s government officials told the BBC in 2012 that they were under pressure from China to accept the Chinese height and therefore had decided to go for a fresh measurement to “set the record straight once and for all.”

In 2019, Nepal’s survey team measured Everest for the first time using GPS on the summit and ground radar to measure the depth of snow and ice. In 2020, China measured Everest from the north side, using BeiDou satellite technology.

The Chinese BeiDou system is China’s independently developed global navigation satellite network a deliberate alternative to the American GPS system. Using BeiDou for the Everest measurement was itself a political statement: China asserting the capability of its own navigation technology on the world’s most visible measurement stage.

The Nepali team did something that made the 2020 measurement historically unique: the survey used GNSS (Global Navigation Satellite Systems) and ground-penetrating radar to measure both the rock height and the snow layer. For the first time, the measurement distinguished precisely between the two determining the snow cap depth at the summit and therefore producing both a rock height and a snow height from a single survey.

“The measurement is within centimetres of accuracy,” said Sushil Dangol, the national coordinator of the Mt Everest Height Measurement Secretariat at the Survey Department. “The data of the survey conducted by Nepali and Chinese measurement teams was processed to calculate the height. The margin of error is within centimetres.”

The result: 8,848.86 metres snow height, including the ice cap, measured by the most sophisticated combination of satellite technology, ground-penetrating radar, and trigonometric calculation ever applied to a mountain summit.

The new measurement is from the rock, not the top of any accumulated snow. Also, it just makes the original measurement even more impressive. Wait. This point requires clarification, because it is where the most confusion exists.

The official announced figure of 8,848.86 metres is the snow height the height including the summit snow cap. The rock height, as measured in 2020, was not officially announced the “rock height” was not announced alongside the joint statement. Nepal’s position that the height should include the snow prevailed in the final joint announcement.

The Political Significance: Nepal Measuring Its Own Mountain

The phrase “its own measurement” appears small. It is not.

From 1856 to 2020 164 years the definitive measurement of Nepal’s most important mountain was conducted by foreign powers. First by British colonial surveyors who did not acknowledge Nepal’s sovereignty over the measurement. Then by the Survey of India. Then by Chinese and American expeditions who measured from their own territory or with their own equipment.

For the first time, Nepal had now conducted its own measurement of the summit. The fact that Nepal’s number prevailed that the snow height was adopted as the official figure was a statement of scientific and political agency that Nepali officials understood explicitly.

“This is a historic day,” Foreign Minister Gyawali said, while making the much-awaited announcement.

The context is important: Nepal is a landlocked country between two of the world’s most powerful nations India and China both of which have historically had disproportionate influence over Nepali political affairs. The Everest measurement was an assertion of technical competence and sovereign authority over a symbol that defines Nepal in the global imagination more than any other. The country that is home to the world’s highest mountain should be the country that measures it.

The joint announcement with China simultaneous statements in Kathmandu and Beijing was also diplomatically significant. It ratified a scientific result that had previously been contested between the two countries, resolving a 15-year dispute between Nepal’s 8,848m and China’s 8,844.43m in a way that gave neither the original figure but honoured both measurement traditions.

Does the Mountain Keep Growing? The Tectonic Reality

Scientists estimate Everest increases in elevation between 0.5 inches to 3 inches (1.27cm–7.6cm) each year.

The Indian tectonic plate is moving northward into the Eurasian plate at approximately 4–5 centimetres per year the same geological process that created the Himalayas 50 million years ago is still ongoing. The Everest massif rises slowly, year by year, as the collision continues. The rate of uplift is partially offset by erosion wind, ice, and rock fall that strips the summit surfaces.

The 2015 Gorkha Earthquake which killed nearly 9,000 people in Nepal introduced another variable. The 2015 earthquake is thought to have reduced the elevation by 1 inch (2.54 centimetres). Major seismic events can both raise and lower mountain elevations depending on their mechanism and the specific stress they relieve in the local geology.

The practical implication: 8,848.86 metres is the most accurate measurement ever taken of Everest’s height and it is already slightly wrong, because the mountain has moved since December 2020. The number in the textbooks is always, by geological definition, out of date. The question is how wrong it is, not whether it is wrong.

Yes, Mount Everest’s height is not fixed. It never was. The number we give it is a snapshot of a moving target, taken with the best instruments available, by the most qualified surveyors operating, and agreed upon by the two nations that matter most politically. It is accurate to within centimetres. It will require re-measurement within a generation.

What This Means for Climbers and Trekkers

For the climber who has summited Everest, the difference between 8,848m and 8,848.86m is the length of a desk. You climbed exactly as high. The certificate you hold, the memory you carry, the achievement you completed none of these change by 86 centimetres.

For the trekker arriving at Everest Base Camp (5,364m), the new official height changes nothing practical. Base camp is still the same glacial flat. Kala Patthar (5,545m) still offers the same Everest panorama. The Khumbu Icefall is still the most dangerous section of the standard route.

What the new number changes is the story. The 8,848.86m figure is a Nepali measurement, jointly confirmed with China, produced with the best technology available, announced on a historic day in Kathmandu by Nepal’s own foreign minister. Every climber who reaches the summit now stands on a height that Nepal itself measured.

For a country that has always been defined by this mountain in the eyes of the world, that matters more than 86 centimetres.

The Measurement Timeline at a Glance

Explore All About Nepal is based in Kathmandu in the country that measured this number. For context on climbing and trekking in the Everest region, read our related guides below.