Calibrated airspeed from true airspeed or Mach

The calibrated airspeed to fly for a true airspeed or Mach number at a pressure altitude and temperature, with Mach, EAS, and impact pressure.

Go the other way: True airspeed from indicated or calibrated airspeed →

Planning and education aid. Not for primary navigation. Full disclaimer

Experimental: not yet fully verified. How results are checked

Computing your own values needs JavaScript and WebAssembly. The worked example below was computed when this page was built, and the documentation under "How we got this" applies.

264.4kt

Fly 264.4 kt calibrated for Mach 0.78. That is 449.6 kt true.

Mach
True airspeed
Equivalent airspeed
Impact pressure qc
Speed of sound
Dynamic pressure q

Provenance

Computed by: aviation.airspeed.tas-to-cas 1.0.0, core 0.1.0
Model: TAS → Mach at the outside air temperature → impact pressure at the static pressure → CAS by the sea-level relation; Rayleigh pitot formula above Mach 1
Accuracy: Exact compressible-flow relations for γ = 1.4 air to double precision. Planning aid, not certified for navigation.
Notes: 1 shown with the answer
Cites: William Gracey, NASA Langley Research Center, Measurement of Aircraft Speed and Altitude, NASA Reference Publication 1046; International Civil Aviation Organization, Manual of the ICAO Standard Atmosphere (extended to 80 kilometres (262 500 feet))

Something look off?

Your values

Showing an example. Change anything.

True airspeedoptional Like 288.6 kt; or give Mach instead · plain numbers mean kt Machoptional Like 0.78; or give TAS instead Pressure altitude Like 10000 ft (altimeter set to 29.92 inHg or 1013.25 hPa) · plain numbers mean ft Outside air temperatureoptional Static air temperature, like -5 °C · plain numbers mean °C

More options 6

Temperature sourceoptional measured (default) or isa to assume the standard temperature VS0, stall speed in the landing configurationoptional Bottom of the white arc, like 48 kt · plain numbers mean kt VS1, stall speed cleanoptional Bottom of the green arc, like 55 kt · plain numbers mean kt VFE, maximum flaps extendedoptional Top of the white arc, like 95 kt · plain numbers mean kt VNO, maximum structural cruisingoptional Top of the green arc, like 130 kt · plain numbers mean kt VNE, never exceedoptional The red line, like 160 kt · plain numbers mean kt

Run many at once from a CSV

Loading…

How we got thisFormula, worked example, sources, and proof

Model: TAS → Mach at the outside air temperature → impact pressure at the static pressure → CAS by the sea-level relation; Rayleigh pitot formula above Mach 1

Accuracy: Exact compressible-flow relations for γ = 1.4 air to double precision. Planning aid, not certified for navigation.

Worked example: Mach 0.78 at FL350. Source: Round trip of the add-aviation-suite FL350 scenario (Gracey RP-1046 equations). It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

You enter

Mach: 0.78
Pressure altitude: 35000 ft
Outside air temperature: -54.3 °C

You get

Calibrated airspeed: 264.4 kt
Mach: 0.78
True airspeed: 449.6 kt
Equivalent airspeed: 250.3 kt
Impact pressure qc: 117.94 hPa
Speed of sound: 576.5 kt
Dynamic pressure q: 101.54 hPa
Compressibility correction: 14.1 kt
Flow branch: subsonic (isentropic)

Review: Not yet independently reviewed by a flight instructor (CFI).

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.0.0, core 0.1.0. See this tool in the verification report.

Checked against: 6 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

Measurement of Aircraft Speed and Altitude, NASA Reference Publication 1046, William Gracey, NASA Langley Research Center, NASA RP-1046. Chapter 2 (airspeed equations: subsonic and Rayleigh supersonic pitot relations) and Chapter 16 (temperature).
Manual of the ICAO Standard Atmosphere (extended to 80 kilometres (262 500 feet)), International Civil Aviation Organization, 3rd edition, Doc 7488/3. Section 2 (defining constants and equations) and Table 1. Paid only.

Terms

ISA: International Standard Atmosphere: A reference atmosphere: 15 °C and 1013.25 hPa at sea level, cooling 6.5 °C per kilometer up to 11 km. Altimeters and performance charts are built on it. Source: Manual of the ICAO Standard Atmosphere (Doc 7488)
VFE: maximum flap extended speed: The fastest speed at which the flaps may be extended. It is the top of the white arc on the airspeed indicator. Source: Pilot's Handbook of Aeronautical Knowledge
VNE: never exceed speed: The speed never to be exceeded in any operation. It is the red line on the airspeed indicator. Source: Pilot's Handbook of Aeronautical Knowledge
VNO: maximum structural cruising speed: The fastest speed for normal operation. Above it, in the yellow arc, fly only in smooth air. Source: Pilot's Handbook of Aeronautical Knowledge
VS0: stall speed in the landing configuration: The slowest speed at which the aircraft still flies with the flaps and gear down. It is the bottom of the white arc on the airspeed indicator. Source: Pilot's Handbook of Aeronautical Knowledge
VS1: stall speed in a stated configuration: The slowest speed at which the aircraft still flies in the clean configuration. It is the bottom of the green arc on the airspeed indicator. Source: Pilot's Handbook of Aeronautical Knowledge

Experimental means this tool has not yet met the stable bar: at least 20 golden vectors, differential tests, and an independent worked example.