What is True Airspeed (TAS)?

True Airspeed (TAS) is the actual speed at which an aircraft moves through the air mass it is flying in. While your Indicated Airspeed (IAS) is what you see on your cockpit instruments, it is subject to errors caused by changes in air density. As an aircraft climbs higher, the air becomes thinner (less dense). Because the airspeed indicator relies on ram air pressure, it under-reads at higher altitudes.

TAS is a critical metric for flight planning and navigation because it represents the actual performance of the aircraft. When combined with wind speed and direction, TAS allows pilots to calculate Ground Speed (GS), which determines how long it will take to reach a destination.

How to Calculate True Airspeed

The standard rule of thumb used by pilots is that TAS increases by approximately 2% for every 1,000 feet of altitude above sea level. However, for precise navigation, pilots must account for non-standard temperatures. Our calculator uses the atmospheric density ratio to provide a more accurate TAS value.

To use this tool, simply input your Indicated Airspeed, your current Pressure Altitude, and the Outside Air Temperature (OAT). The calculator determines the density altitude and applies the correction factor to give you your True Airspeed in either knots or miles per hour.

Difference Between IAS, TAS, and Ground Speed

Understanding the difference between the various types of airspeed is essential for aviation safety and efficiency:

• Indicated Airspeed (IAS): The raw reading from the airspeed indicator. It is vital for maintaining safe aerodynamic flight (stalls, flaps, and gear speeds).
• True Airspeed (TAS): IAS corrected for altitude and non-standard temperature. This is how fast you are actually moving through the air.
• Ground Speed (GS): TAS corrected for wind. If you have a tailwind, your GS will be higher than your TAS. If you have a headwind, it will be lower.

Frequently Asked Questions

Why does TAS increase with altitude?
As you climb, air density decreases. There are fewer air molecules to push against the pitot tube for a given speed. To generate the same pressure (IAS) that you would at sea level, the aircraft must move faster through the thinner air.

Is TAS the same as Ground Speed?
Only in zero-wind conditions. Ground speed is the speed of the aircraft relative to the ground, while TAS is relative to the air around it.