How many miles does oxygen exist above the earth?

Well, you can't breathe properly at about five miles up, near the peak of mount Everest. The formal definition of space is around 62 miles (100km). You don't want to orbit there, though, as the atmosphere is still thick enough to cause rapid decay. The ISS orbits just shy of 250 miles. read more

The chemical composition of the atmosphere is almost uniform up to the mesopause, around 80 km above the Earth surface, so that up to the mesopause you have about 20% of oxygen (23% if you consider weight and not molecules). read more

Not only would every human on earth die, but most animals on earth would die as well. Also consider the ecological effects of a sudden mass extinction. Another important factor would be the change in atmospheric pressure. Since oxygen makes up 21% of the atmosphere it should become significantly lighter. read more

Air surrounds Earth and becomes thinner farther from the surface. Roughly 100 miles (160 km) above Earth, the air is so thin that satellites can zip through with little resistance. Still, traces of atmosphere can be found as high as 370 miles (600 km) above the surface. read more

The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause. This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft). read more