To compute IAS (Indicated Air Speed) from TAS (True Air Speed), Pressure Altitude (air density) and temperature are considered. To this end, first a correction to the TAS for the air density/pressure is applied, then a correction for temperature is applied based on the difference between the OAT (Outside Air Temperature) and the ISA temperature at the given altitude. This calculation makes use of the ISA 1976 atmospheric model.
Note: this calculator is not suitable for supersonic speeds i.e. greater than the speed of sound.
