KATHMANDU, Nepal — Mount Everest is the tallest mountain in the world, but precisely how tall is it?

It’s not such a simple question.

In the past, geologists have disagreed about what to include in their calculations: Should the summit’s snowcap be included? Or should surveyors drill down to the peak’s rock base?

What about the recent earthquakes in Nepal, which geologists believe shrunk the mountain by about three centimeters, or a little more than an inch? Or the fact that wind speed affects how much snow covers the summit at any given time?

Then there is the challenge of geography: Reaching the summit of Everest is only possible a few weeks each year, and measuring the mountain’s height from sea level has presented difficulties in the past. (Landlocked Nepal is a long way from the nearest shore.)