True Airspeed Calculator
Fill in the values and the answer updates as you type.
How the True Airspeed Calculator works
The density ratio σ = (pressure ÷ sea-level pressure) ÷ (temperature ÷ 288.15 K). True airspeed ≈ calibrated airspeed ÷ √σ. This treats calibrated airspeed as equivalent airspeed, which is a good approximation below about 250 kt and 10,000 ft. The rule of thumb adds about 2% of TAS for every 1,000 ft of altitude. Use your flight computer or aircraft manual for precise navigation. Example: with Calibrated airspeed 110 kt, Pressure altitude 8000 ft, and Outside air temperature 5 °C, the result is True airspeed (kt) = 125.4; True airspeed (km/h) = 232; Density ratio = 0.7695.
Inputs and results
The True Airspeed Calculator takes 3 inputs and gives 4 results.
What you enter
- Calibrated airspeed (kt) — starts at 110.
- Pressure altitude (ft) — starts at 8000.
- Outside air temperature (°C) — starts at 5.
What you get
- True airspeed (kt)
- True airspeed (km/h)
- Density ratio
- Rule of thumb TAS (kt)
Example: True Airspeed Calculator with the starting values
With calibrated airspeed 110 kt, pressure altitude 8000 ft and outside air temperature 5 °C, the calculator returns:
| True airspeed (kt) | 125.4 |
|---|---|
| True airspeed (km/h) | 232 |
| Density ratio | 0.7695 |
| Rule of thumb TAS (kt) | 127.6 |
Change any value above and the results update straight away.
True Airspeed Calculator FAQ
How do I use the True Airspeed Calculator?
Enter calibrated airspeed, pressure altitude and outside air temperature in the fields, then read true airspeed (kt), true airspeed (km/h), density ratio and rule of thumb tas (kt) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the True Airspeed Calculator calculate?
True airspeed from calibrated airspeed, pressure altitude, and temperature. It returns true airspeed (kt), true airspeed (km/h), density ratio and rule of thumb tas (kt) from the 3 values you provide.
What values does the True Airspeed Calculator start with?
It opens with calibrated airspeed 110 kt, pressure altitude 8000 ft and outside air temperature 5 °C so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the True Airspeed Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the True Airspeed Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.