How many miles away from earth does the thermosphere end?

Answer 1

The thermosphere is what we call the layer between the mesosphere and

the exosphere. We associate that name with the region of the atmosphere

between altitudes of 90 to 1,000 km (56 to 621 miles).

Answer 2

The thermosphere technically does not have a defined boundary where it ends. It gradually transitions into the exosphere, which is the outermost layer of Earth's atmosphere. The exosphere can extend hundreds of miles into space.