Velocity Conversion (IAS/EAS/TAS)
Aerodynamics / Flow Properties
Table of Contents
About this calculator
Velocity Conversion (IAS/EAS/TAS) converts between common airspeed definitions using local ISA density at the selected altitude.
Use IAS for cockpit-style low-speed indicated airspeed inputs, EAS for dynamic-pressure-equivalent speed, or TAS for actual air-relative flight speed.
This model uses the standard EAS-TAS density-ratio relation and treats IAS as approximately equal to EAS unless a separate compressibility correction model is applied.
Inputs
Enter the required values used in the formula for Velocity Conversion (IAS/EAS/TAS).
IAS is treated as approximately equal to EAS in this incompressible ISA-based model.
Required inputs for calculation
Default values are prefilled where applicable. You can overwrite them.
- Velocity (m/s) - Input airspeed magnitude in the selected airspeed definition
- Altitude (h) (m) - ISA altitude above mean sea level used to compute local air density
Results
Results are hidden until you click Calculate.
Formula used for calculations
V_EAS = V_TAS * sqrt(rho / rho0)
Inverse relation
V_TAS = V_EAS / sqrt(rho / rho0)
rho0 = 1.225 kg/m^3
IAS treatment in this model
At low speeds, IAS is treated as approximately equal to EAS.
Compressibility and instrument corrections are not included.
Atmosphere model
Density rho is computed from ISA altitude.
All outputs are tied to the selected altitude and resulting local atmospheric density.
This airspeed conversion uses ISA density at altitude together with the standard EAS-TAS density-ratio relation. It is intended for incompressible or low-Mach workflows, with IAS approximated as EAS unless a separate compressibility correction model is used.
Assumptions
- Altitude is interpreted using the ISA atmosphere and local density is computed from that altitude.
- The EAS-TAS conversion uses the incompressible density-ratio relation with rho0 = 1.225 kg/m^3.
- IAS is treated as approximately equal to EAS, so compressibility and instrument corrections are not included.
Recommendations
- Use IAS input only for low-speed work where IAS approximately equals EAS.
- At estimated Mach above about 0.3, treat the IAS output as approximate because compressibility corrections are not included.
- Use the selected altitude carefully, since all EAS-TAS conversion is tied to the ISA density at that altitude.
FAQs
How does this calculator treat IAS?
IAS is treated as approximately equal to EAS, which is appropriate for low-speed incompressible work. Instrument and compressibility corrections are not included.
What atmosphere model is used?
The calculator uses ISA altitude to compute local density, then converts between EAS and TAS with the standard density-ratio relation.
When should I use a more advanced model?
If the estimated Mach number is above about 0.3 or you need calibrated or compressible airspeed corrections, use a higher-fidelity air-data model instead of the IAS approximation here.