Where is the ceiling or end of the atmosphere?

The Earth's atmosphere doesn't have a definitive boundary, but it gradually thins out with altitude. The Kármán line, located at about 100 kilometers (62 miles) above sea level, is commonly used to define the boundary between the atmosphere and outer space. Above this line, the atmosphere becomes too thin to support conventional flight. However, atmospheric layers extend beyond this point, with traces of gases present even at higher altitudes.