Air Pressure at Altitude Fomula:
  p = p₀e^-(h/h₀)

Where:

  p: Atmospheric pressure, in Pa
  p₀: Atmospheric Pressure at Sea Level, in Pa
  h: Height (Altitude), in meter
  h₀: Scale Height, in meter

Note: The surface pressure on Earth is approximately 1 bar, and the scale height of the atmosphere is approximately 7 kilometers.