Air Pressure At Altitude
Calculate air pressure at any altitude using the barometric formula. Get pressure in Pa, atm, and hPa with interactive charts. Free online calculator for aviation, hiking, and physics.
About This Calculator
The Air Pressure At Altitude Calculator computes atmospheric pressure at any elevation using the barometric formula. This tool is essential for pilots, mountaineers, meteorologists, physics students, and anyone who needs to understand how air pressure changes with altitude. The calculation accounts for both altitude and temperature, giving you accurate pressure readings in pascals (Pa), atmospheres (atm), and hectopascals (hPa).
The barometric formula used is P = P₀ × exp(−g × M × h / (R × T)), where P₀ is the sea level pressure (default 101,325 Pa), g is gravitational acceleration (9.80665 m/s²), M is the molar mass of Earth's air (0.0289644 kg/mol), h is the altitude in meters, R is the universal gas constant (8.314 J/(mol·K)), and T is the temperature in Kelvin. The result shows how atmospheric pressure decreases exponentially as you gain altitude.
Regional Notes
International: The standard atmosphere model used here (ISA — International Standard Atmosphere) is globally recognized. The default sea level pressure of 101,325 Pa (1 atm) is the international standard regardless of region. Temperature defaults vary: 15°C for India/UK temperate zones and 20°C for US warmer zones, but you should enter the actual temperature at your target altitude for the most accurate result.
Frequently Asked Questions
What is the barometric formula?
The barometric formula P = P₀ × exp(−g × M × h / (R × T)) describes how atmospheric pressure decreases with altitude. P₀ is sea level pressure, g is gravity (9.80665 m/s²), M is molar mass of air (0.0289644 kg/mol), h is altitude, R is the universal gas constant (8.314 J/(mol·K)), and T is temperature in Kelvin.
How does air pressure change with altitude?
Air pressure decreases exponentially with altitude. At 1,000 m, pressure is about 90% of sea level; at 5,500 m, it drops to about 50%; and at the summit of Mount Everest (8,849 m), pressure is only about 30% of sea level pressure. The decrease follows the barometric formula and depends on temperature as well.
What is standard sea level pressure?
Standard sea level pressure is defined as 101,325 Pa (pascals), which equals 1,013.25 hPa, 1 atm (atmosphere), 29.92 inHg, or 14.70 psi. This value is used as the reference pressure P₀ in the barometric formula and represents the average atmospheric pressure at sea level on Earth.
Why does temperature affect air pressure at altitude?
Temperature affects air density and molecular motion. Warmer air expands and rises, creating a slower pressure drop with altitude. Colder air is denser, causing pressure to decrease more rapidly. The barometric formula accounts for this through the temperature term in the exponent — lower temperature means a larger exponent magnitude and faster pressure decay.
At what altitude is an airplane cabin pressurized to?
Commercial aircraft cabins are pressurized to maintain an equivalent altitude of about 1,800 to 2,400 m (5,900 to 8,000 ft), corresponding to a pressure of 0.75 to 0.81 atm. This is a compromise between structural weight limits and passenger comfort. The pressurization gradually changes during takeoff and landing.
How does altitude affect boiling point of water?
Water boils at a lower temperature at higher altitudes because atmospheric pressure is lower. At sea level (101,325 Pa), water boils at 100°C. At 2,000 m, pressure drops to about 80,000 Pa and water boils at approximately 94°C. At 4,000 m, with pressure around 64,000 Pa, the boiling point is only about 87°C.
What is the air pressure at the summit of Mount Everest?
At the summit of Mount Everest (8,849 m), the air pressure is approximately 31,000 to 33,000 Pa, which is about 0.3 to 0.33 atm. This is in the 'death zone' where human survival without supplemental oxygen is extremely limited. At -30°C, using the barometric formula, the pressure calculates to about 0.28 atm.
Is this calculator accurate for weather forecasting?
This calculator uses the standard barometric formula which gives a good approximation for the International Standard Atmosphere. However, real-world weather systems, humidity, and local geography can cause deviations. For precise aviation or scientific use, always consult current meteorological data and local pressure readings.