ISA Deviation Calculator
Compare the outside air temperature with the ISA standard temperature at a pressure altitude.
Description
Compare the outside air temperature with the ISA standard temperature at a pressure altitude.
ISA Deviation Calculator provides a focused, reproducible calculation with explicit inputs and a deterministic result. Compare the outside air temperature with the ISA standard temperature at a pressure altitude.
Use to compare observed temperature with the ISA tropospheric temperature at pressure altitude.
When to use ISA Deviation Calculator
Use to compare observed temperature with the ISA tropospheric temperature at pressure altitude.1
How the calculation works
Compare the outside air temperature with the ISA standard temperature at a pressure altitude.2
ISA deviation = OAT − [15°C − 1.9812°C per 1000 ft × pressure altitude] Inputs and interpretation
Keep every input on the same valuation, timing, unit, and assumption basis. Interpret the output at the precision supported by those inputs rather than treating extra decimal places as additional certainty.
Limitations and assumptions
The linear lapse model is limited to the lower atmosphere and ISA deviation alone is not density altitude or a performance result.
References
-
Pilot's Handbook of Aeronautical Knowledge — Federal Aviation Administration
-
International Standard Atmosphere — Wikipedia contributors
Similar or alternative tools
- Density Altitude ISA Correction Calculator
Estimate density altitude from pressure altitude and outside air temperature using the ISA lapse rate.
- ISA Deviation Calculator
Compute how much the outside air temperature deviates from ISA at the altitude.
- Density Altitude Calculator
Compute density altitude from pressure altitude and outside air temperature.