True Airspeed Calculator
Clear airspeed calculations with consistent units.
Enter calibrated airspeed after applying the aircraft IAS correction. This subsonic calculation includes compressibility; IAS is not automatically CAS. Use static OAT, not uncorrected total air temperature.
Formula & operating range
Pressure altitude uses indicated altitude + 1,000 × (29.92 − QNH inHg). ISA pressure is evaluated at that altitude. CAS yields sea-level-equivalent impact pressure; the subsonic isentropic relation yields Mach, then TAS = Mach × √(1.4 RT). Density altitude inverts the dry ISA density model; it differs from the 120 ft/°C approximation used in the separate density-altitude tool.
Dry, calorically perfect air model. ISA altitude range −1,000 to 20,000 metres; actual temperature −100 to 60 °C. TAS conversion is restricted to subsonic Mach, QNH 25–35 inHg and indicated altitude −2,000 to 60,000 ft. No humidity, instrument error or total-temperature correction is applied.
NASA: speed of sound and isentropic relations