✈️ True Airspeed Calculator
Convert calibrated (indicated) airspeed into true airspeed based on your altitude and the outside air temperature.
What This Calculator Does
Calibrated airspeed (roughly what an airspeed indicator shows) differs from true airspeed — the aircraft’s actual speed through the air — because air density drops with altitude and temperature. This calculator converts CAS to TAS using pressure altitude and outside air temperature.
The Formula
The pressure ratio is calculated from the standard atmosphere as δ = (1 − 6.8756×10⁻⁶ × altitude)^5.2559 for altitudes below 36,089 ft. The temperature ratio is θ = (OAT in Kelvin) / 288.15, giving a density ratio σ = δ/θ. True airspeed is then TAS = CAS / √σ.
Note: This method neglects compressibility effects, which become significant above roughly 300 knots or at high altitude — it’s accurate enough for typical light aircraft speeds and general flight planning education.