Mont Blanc Survey Puts Summit at 4,807.47 Metres

French surveyors measured the snow-covered summit of Mont Blanc at 4,807.47 metres above sea level during an expedition in mid-September 2026. That figure sits 1.88 metres above the 4,805.59 metres recorded in 2023, the lowest modern reading in the series that began in 2001.

The team of 32 surveyors, mountain guides and technical specialists reached the summit at daybreak on 17 September. They carried roughly 30 kilograms of equipment and spent more than two hours taking readings. The Haute-Savoie Departmental Chamber of Surveyors organised the campaign, as it has done at intervals since 2001.

Jean des Garets, president of the chamber, said the summit remains in constant motion. Individual measurements do not by themselves prove the effects of global warming. They supply data points that can be compared over longer periods.

The altitude change comes from the thickness of the snow and ice cap that sits on the rock. Wind, snowfall and temperature reshape that cap from one season to the next. The surveyors also used ground-penetrating radar this year to map the ice and the rocky peak beneath it.

Earlier unpublished readings show the summit stood at 4,808.51 metres in 2024 and 4,808.76 metres in 2025. The 2026 figure is therefore higher than 2023 but lower than those two intervening measurements. Between 2000 and 2010 the peak was repeatedly measured near 4,810 metres. The highest modern reading was 4,810.90 metres in 2007.

The 1894 measurement by Joseph and Henri Vallot placed the summit close to the current figure. The latest reading lies roughly 27 centimetres above that late-nineteenth-century value. Glaciologists in Grenoble have noted that the summit sits high enough and remains cold enough that its ice rarely melts. Over the twentieth century its thickness changed by only a few metres.

The measurement campaign began in 2001 at 4,810.40 metres. Since then the chamber has released public figures every two or three years. The 2021 reading was 4,807.81 metres. The 2023 low of 4,805.59 metres prompted concern at the time. Surveyors have stressed that a single reading does not settle questions about climate effects on the peak.

Mont Blanc sits on the border between France and Italy, between Haute-Savoie and the Aosta Valley. It remains the highest summit in the Alps and in Western Europe. The rock elevation itself changes far more slowly than the snow and ice cover. The surveyors' work tracks the surface that climbers actually stand on.

The data series now stretches across more than two decades. Scientists can use the accumulating measurements to study how weather patterns redistribute snow at extreme altitude. The chamber has said the long-term record will help separate short-term weather effects from any slower shifts.

Expedition members worked in eleven rope teams. They combined satellite positioning, photogrammetry and the new radar readings. The official margin of precision for the 2026 figure is about 10 centimetres. The chamber presented the results in Saint-Gervais-Mont-Blanc on 14 October.

Climbers and guides who reach the summit in coming seasons will stand on a surface roughly two metres higher than the one measured three years earlier. The rock beneath that surface has not risen by that amount. The difference is ice and snow that arrived, settled and was shaped by wind.