How to Use the Atmospheric Pressure by Altitude Calculator
Atmospheric pressure is the force exerted by the weight of the air above a given point on Earth's surface. At sea level (0m), standard atmospheric pressure is defined as 1013.25 hPa (760 mmHg, 1 atm), but as altitude increases, there's less air stacked above you, so pressure keeps decreasing. This relationship isn't linear - it decreases exponentially, dropping gently at lower altitudes and more steeply at higher ones.
This calculator uses the International Standard Atmosphere (ISA) barometric formula, P = P0 x (1-2.25577x10^-5 x h)^5.25588, to calculate the atmospheric pressure at a given altitude in hPa, mmHg, and atm simultaneously. At 1,000m, for example, pressure drops to about 899 hPa, and at 3,000m it drops to about 701 hPa - roughly 30% lower than sea level.
Useful for checking pressure changes during hiking or trekking, calculating the pressure-altitude relationship for meteorology or aviation coursework, or understanding why airplane cabin pressure is kept lower than sea-level pressure. Enter an altitude to see results in all three units instantly.
Frequently Asked Questions
Standard atmospheric pressure at sea level (0m) is 1013.25 hPa, 760 mmHg, or 1 atm. This is the reference point of the International Standard Atmosphere (ISA) model, and pressure decreases from this value as altitude increases.
Airliners don't keep the cabin at outside pressure while cruising at 10-12km. Instead, they pressurize the cabin to roughly the pressure found at 1,800-2,400m elevation (about 750-800 hPa). That pressure difference is why your ears pop or your body feels puffy during a flight.