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Aviation
True Airspeed Calculator
Estimate true airspeed from calibrated airspeed, altitude and temperature.
True airspeed
—
TAS.
| Density altitude | — |
|---|---|
| CAS | — |
| Correction | — |
| — |
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Enter your figures above to see the step-by-step working.
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How the True Airspeed Calculator Works
Your airspeed indicator shows calibrated airspeed, which reads low at altitude because the air is thinner. True airspeed — your actual speed through the air mass — is higher. A reliable rule of thumb adds about 2% to the calibrated airspeed for every 1,000 feet of density altitude.
Enter calibrated airspeed, pressure altitude and temperature; the calculator works out the density altitude and applies the 2%-per-1,000-ft correction. It’s an approximation — good for flight planning, though an E6B or air-data computer is more precise.
TAS ≈ CAS × (1 + 0.02 × density altitude ÷ 1000)
Frequently Asked Questions
What is true airspeed?
Your actual speed relative to the surrounding air, as opposed to the indicated or calibrated airspeed shown in the cockpit, which reads low at altitude.
How do you estimate TAS?
Add about 2% to the calibrated airspeed for each 1,000 feet of density altitude.
Is this exact?
It’s a close approximation used for planning. An E6B flight computer or air-data system gives a more precise figure.
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