Divergent views in the past with respect to including snowcaps or not meant that China had a different height from Nepal over Mount Everest. Not anymore!
The earthquake that occurred in Mount Everest in 2015 necessitates this harmonized quest.
The official height for Mount Everest is now 8,848.86metres.

What about Kilimanjaro

Though Everest is the highest mountain, it isn’t the tallest mountain.

Mauna Kea is taller than Everest, but Everest is higher

F*** China.

The highest mountains above sea level are generally not the highest above the surrounding terrain. There is no precise definition of surrounding base, but Denali, Mount Kilimanjaro and Nanga Parbat are possible candidates for the tallest mountain on land by this measure. The bases of mountain islands are below sea level, and given this consideration Mauna Kea (4,207 m (13,802 ft) above sea level) is the world's tallest mountain and volcano, rising about 10,203 m (33,474 ft) from the Pacific Ocean floor. Ojos del Salado has the greatest rise on Earth: 13,420 m (44,029 ft) vertically to the summit from the bottom of the Atacama Trench, which is about 560 km (350 mi) away, although most of this rise is not part of the mountain.

The highest mountains are also not generally the most voluminous. Mauna Loa (4,169 m or 13,678 ft) is the largest mountain on Earth in terms of base area (about 2,000 sq mi or 5,200 km2) and volume (about 10,000 cu mi or 42,000 km3), although, due to the intergrade of lava from Kilauea, Hualalai and Mauna Kea, the volume can only be estimated based on surface area and height of the edifice.