Aviation Calculators
True airspeed.
True airspeed (TAS) is calibrated airspeed corrected for altitude and nonstandard temperature, so it climbs above CAS as the air thins. Enter calibrated airspeed, pressure altitude and outside air temperature to get TAS and Mach number. Runs in your browser; nothing is sent or stored.
Planning aid, not for flight operations
This tool is for study, trip planning and curiosity. It is not approved flight-planning or performance data. For an actual flight, use the aircraft's approved Pilot's Operating Handbook or Aircraft Flight Manual, current weather and charts, and your own judgement as pilot in command. Results can differ from your aircraft's real figures.
Inputs
Result
Fill the form and press Calculate.
Worked example
CAS 100 knots at a pressure altitude of 8,000 ft and an outside air temperature of 5 °C (+5.8 °C against standard). The air density is 76.9% of sea level, the speed of sound is 649.9 knots and the Mach number is 0.175, so the true airspeed is 113.9 knots (131.1 mph). The quick estimate CAS ÷ √σ gives 114.0 knots.
How it works
CAS is defined from the impact pressure the pitot tube measures, using standard sea-level pressure and speed of sound. The tool inverts that definition: impact pressure qc ÷ P0 = (1 + 0.2 × (CAS ÷ a0)2)3.5 − 1, with a0 = 340.294 m/s (ICAO standard value) = 661.48 knots (Wikipedia rounds this to 1,225 km/h = 661.45 kn) and P0 = 1013.25 hPa. The static pressure at your pressure altitude comes from the standard atmosphere.
Then Mach = √(5 × [(qc ÷ p + 1)2/7 − 1]) and TAS = Mach × a, where the speed of sound a = 661.48 × √(T ÷ 288.15 K). This includes compressibility and is valid below Mach 1. The estimate CAS ÷ √σ (density ratio σ) ignores compressibility and is shown for comparison.
Wind is not included. TAS is speed through the air, not over the ground; use the Wind Correction Angle and Ground Speed Calculator for that.
Sources (each opened 2026-10-08): FAA, Pilot's Handbook of Aeronautical Knowledge, Chapter 8: Flight Instruments; Wikipedia, Calibrated airspeed (calculation from impact pressure); Wikipedia, International Standard Atmosphere.
FAQ
What is true airspeed?
The FAA handbook defines true airspeed as CAS corrected for altitude and nonstandard temperature. Because air density decreases with altitude, an aircraft has to move faster through thinner air to produce the same dynamic pressure.
What is the difference between IAS, CAS and TAS?
IAS is what the airspeed indicator shows. The FAA handbook defines CAS as IAS corrected for installation and instrument error, and says that in cruising and higher airspeed ranges IAS and CAS are approximately the same. TAS is then CAS corrected for altitude and temperature.
Why is my TAS higher than my indicated airspeed at altitude?
The indicator responds to impact pressure, which depends on air density. At altitude the air is less dense, so the same indicated airspeed means a higher true airspeed.
Does this include wind?
No. True airspeed is speed through the air. Ground speed also depends on wind; see the Wind Correction Angle and Ground Speed Calculator.
What if the result says Mach 1 or more?
This tool uses the subsonic relationship only, so it stops when the speed reaches Mach 1.
Is this for flight planning?
It is a learning and planning aid. Use your aircraft's approved performance data and a calibrated flight computer or avionics for real operations.