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Calcimator

Airspeed Converter

Convert between IAS, CAS, EAS, TAS, and Mach number at any altitude and temperature. Also shows mph and km/h equivalents.

Inputs

kt
ft

GA cruise: 3,000–12,000 ft, Airline: FL250–FL410

°F

Results

Indicated Airspeed (IAS)

120 kt

True Airspeed (TAS)

129 kt

Mach Number

0.199

Calibrated Airspeed (CAS)120 kt
Equivalent Airspeed (EAS)109 kt
TAS (mph)149 mph
TAS (km/h)239 km/h
How to Use This Calculator
  1. Select which airspeed type you want to convert from (IAS, CAS, TAS, or Mach).
  2. Enter the speed value.
  3. Enter pressure altitude and outside air temperature.
  4. All equivalent airspeeds are calculated instantly.

How the result changes with Speed

SpeedIndicated Airspeed (IAS)True Airspeed (TAS)Mach Number
140140 kt158 kt0.246
0.78250 kt450 kt0.78
6565 kt68 kt0.104

What each input means

Convert From
Select which airspeed type you're starting from.
Speed
Enter the airspeed value. For Mach, enter as decimal (e.g., 0.78).
Pressure Altitude
Altitude with altimeter set to 29.92 inHg.
Outside Air Temperature
Outside air temperature at your altitude.

How this is calculated

Worked example, using the default values

  1. Density Ratio (σ)
    σ = Pressure Ratio ÷ Temperature Ratio
    0.8320 ÷ 0.9653 = 0.8620
  2. Speed of Sound
    a = 38.967 × √(T in Kelvin)
    38.967 × √278.1 = 650 kt
  3. Converting from IAS
    TAS = CAS ÷ √σ
    120 ÷ √0.8620 = TAS = 129 kt

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