Air Data Calculations

Posted in engineering by Christopher R. Wirz on Sat Jun 11 2011

Standard Atmosphere Computations

This form uses JavaScript to compute properties related to the 1976 standard atmosphere up to 230,000 ft. Standard day assumes a pressure of 101,325 pascals (14.6959 psi) (1 atm), a temperature of 15 °C (59 °F), a temperature lapse rate of −6.5 °C (20.3 °F) per km (roughly −2 °C (-3.6 °F) per 1,000 ft), and a density of 1.2250 kilograms per cubic meter (0.07647 lb/cu ft) at mean sea level.

The ISA calculations then assume the column of air is providing that pressure, and adjusts the pressure as altitude increases to account for the column of air effectively being smaller at higher altitudes.


Imperial Units Metric Units Aeronautical Units
Altitude ft m
Speed ft/sec m/sec kts
Reference Length ft m


Imperial Units Metric Units
Temperature °R °K
Temperature °F °C
Density sl/ft^3 kg/m^3
Pressure lb/ft^2 N/m^2
Speed of Sound ft/sec m/sec
Viscosity lb sec/ft^2 N sec/m^2
Dynamic Pressure lb/ft^2 N/m^2
Mach Number
Critical Cp
Vacuum Cp
Reynolds Number
Laminar Cf
Turbulent Cf

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