Standard Atmosphere (ISA) Calculator
Look up ISA standard atmosphere values at any altitude: temperature, pressure, density, density ratio, and speed of sound.
Inputs
ft
Troposphere: 0–36,089 ft, Stratosphere: 36,089–65,617 ft
Results
ISA Temperature
74.05°F
Pressure
696.8 hPa
ISA Temperature23.3°F
Pressure20.58 inHg
Density Ratio (σ)0.7385
Air Density0.9046 kg/m³
Speed of Sound638 kt
Pressure Ratio (δ)0.6877
Temperature Ratio (θ)0.9312
How to Use This Calculator
- Enter any altitude to see ISA standard atmosphere properties.
- Use ISA temperature to calculate ISA deviation (OAT − ISA temp).
- Density ratio is used in airspeed conversions (TAS = CAS ÷ √σ).
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Related Calculators
Density Altitude Calculator
Calculate density altitude for flight performance planning.
Pressure Altitude Calculator
Field elevation corrected for non-standard pressure.
True Airspeed (TAS) Calculator
Convert IAS to TAS corrected for altitude and temperature.
Airspeed Converter
Convert between all airspeed types: IAS, CAS, TAS, Mach.
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