How does atmospheric pressure change with altitude near Earth’s surface?

Near Earth’s surface, atmospheric pressure decreases as altitude increases. On average, the pressure drops by approximately 3.5 millibars for every 30 meters (100 feet) of elevation.1

This rate of decrease is not constant, however; it can be significantly steeper over cold air because cold air is denser than warmer air. This fundamental relationship—that pressure falls as one climbs—is the principle behind the pressure altimeter, which estimates altitude by measuring the surrounding air pressure.12

The decline in pressure is substantial enough that at heights between 1,500 and 3,000 meters (5,000 to 10,000 feet), the air is thin enough to cause mountain sickness and other physiological challenges in humans.1