Calculate Air Pressure at Altitude
Calculator for the expected air pressure at a target altitude based on the current values. Enter the current air pressure, altitude and temperature, as well as the target altitude and the temperature there. Target altitude pressure is an estimate for normal weather conditions, not for extremes. A less accurate but simpler calculation can be made using the international height formula.
The temperature gradient indicates how quickly the temperature falls with altitude. A good guess in normal weather is 0.0065 °C/meter.
Temperature gradient = ( Temperature at current altitude - Temperature at target altitude ) / Altitude difference
Atmospheric pressure at target altitude = Atmospheric pressure at current altitude * (1-temperature gradient*altitude difference/temperature at current altitude in kelvins)^(0.03416/temperature gradient)