Airspeed Converter

Air density decreases with altitude, and an airspeed indicator reads dynamic pressure rather than true speed through the air -- so at a lower air density, the aircraft has to move faster through the air to generate the same dynamic pressure. That's why, for the same indicated speed, True Airspeed increases as Pressure Altitude increases.

Both push True Airspeed in the same direction (warmer air and higher altitude both mean lower air density), but altitude typically has the larger effect within a normal flight envelope, since pressure drops off faster with altitude than density changes with a realistic temperature range. Both corrections are applied together through the density ratio in this calculator.

Speed sets the starting value that every other airspeed type is derived from, while Pressure Altitude and Outside Air Temperature only apply a correction factor on top of it. A given percentage change in Speed moves every output roughly proportionally, while the same percentage change in altitude or temperature only shifts the correction factor, which is a smaller lever.

Equivalent Airspeed is defined by dynamic-pressure equivalence: EAS = TAS x sqrt(sigma), where sigma is air density relative to sea level. Calibrated Airspeed, by contrast, comes from the aircraft's actual impact pressure through the compressible subsonic relations this calculator applies. At low altitude the two nearly coincide, but as pressure altitude and Mach number climb, the compressibility correction embedded in CAS grows while EAS stays tied to the simple density-ratio relationship, so the gap between them widens. This calculator still treats Indicated Airspeed as equal to Calibrated Airspeed, since it has no instrument or position-error data for your specific aircraft.