Standard temperature variation at different altitudes (up to 105 km)
Sea level temperature
Altitude (H)

Altitude temperature
Sound Speed:
Temperature Ratio:
T (Altitude) / T (Sea level)
Pressure Ratio:
P (Altitude) / P (Sea level)
Density Ratio:
D (Altitude) / D (Sea level)

Definition of standard atmosphere
Definition Values
Pressure altitude
The altitude determined by comparing the ambient pressure of air to the standard pressure of the standard atmosphere.
Density altitude
The altitude determined by measuring the actual air density and comparing it to the standard atmosphere.
Geometric altitude Z
Actual height measured from sea level.
E-earth radius
Geometric altitude
E = 6356.766 km
Geopotential altitude H
Altitude based on the variation in the earth gravity as a function of altitude.
Geopotential altitude
Sea level standard temperature T0 T0 = 288.15 K = 15 ̊C
Standard sea level pressure P0 P0 = 101 325 Pa
Sea level standard density ρ0 = 1.225 kg/m3
Sea level gravitational acceleration g g = 9.806 65 m/s2
Universal gas constant R R = 8.314 47 J/(mol∙K)
Molar mass of dry air M M = 0.028 964 4 kg/mol
Speed of sound c c = 340.3 m/s
Viscosity 1.789∙10-5 (kg∙s)/m
Kinematic viscosity 1.460∙10-5 m2/s
Thermal conductivity 0.025 96 (W∙K)/m
Specific heat Cp Cp = 1005 (J∙K)/kg
Specific heat Cv Cv = 717.98 (J∙K)/kg
Ratio of specific heats 1.4