Use this calculator for flight-planning study or a first-pass cross-check when all inputs describe the same aircraft, atmospheric condition, and phase of flight.

True altitude (ft)

Actual height above the datum.

ISA temperature (°C)

ISA standard temperature at this level.

OAT (°C)

Actual outside air temperature.

Compute what an altimeter would indicate for a known true altitude under non-standard temperature — the inverse of the cold-weather altitude correction. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Indicated altitude (ft)

Uncorrected altimeter indication for these conditions.

Correction (ft)

Signed temperature correction; positive when colder than ISA.

• Do not use a generic calculator in place of the current aircraft flight manual, approved performance data, operating limitations, NOTAMs, weather, or regulations. Real performance changes with configuration, runway condition, altitude, temperature, wind, loading, and technique.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check the result against the aircraft flight manual or approved planning system, then apply the required safety margins. Keep signed wind, heading, altitude, speed, and fuel conventions explicit.

• Altimeter Correction Calculator

  Compute the cold-weather altimeter correction so the altimeter reads true altitude in colder-than-standard air.

• Cold Temperature Correction Calculator

  Estimate the altitude correction for cold temperatures against the ISA atmosphere.

• ISA Deviation Calculator

  Compare the outside air temperature with the ISA standard temperature at a pressure altitude.