Troposphere lapse rate
T = T0 - L x h
L = 6.5 K/km through 11 km
T0 = 288.15 K
Standard atmosphere calculator
Air Temperature vs Altitude Calculator
Calculate International Standard Atmosphere temperature from altitude, with pressure and density shown alongside the temperature result.
Instant ISA temperature solver
Enter altitude
Results update automatically using interpolated International Standard Atmosphere reference values.
Calculated result
Formulas
Air temperature vs altitude formulas used
Unit conversions
degrees C = K - 273.15
degrees F = degrees C x 9 / 5 + 32
m = ft x 0.3048
The calculator interpolates standard-atmosphere temperature values by altitude. ISA represents a reference atmosphere; real outdoor air temperature can differ greatly from standard values.
Reference table
Air temperature by altitude table
| Altitude (km) | Altitude (ft) | Temperature (K) | Pressure (kPa) | Density (kg/m3) |
|---|---|---|---|---|
| 0 | 0 | 288.15 | 101.325 | 1.225 |
| 1 | 3,281 | 281.65 | 89.875 | 1.1116 |
| 2 | 6,562 | 275.15 | 79.495 | 1.0065 |
| 3 | 9,843 | 268.65 | 70.108 | 0.9093 |
| 4 | 13,123 | 262.15 | 61.64 | 0.8194 |
| 5 | 16,404 | 255.65 | 54.02 | 0.7364 |
| 6 | 19,685 | 249.15 | 47.181 | 0.6601 |
| 7 | 22,966 | 242.65 | 41.061 | 0.59 |
| 8 | 26,247 | 236.15 | 35.6 | 0.5258 |
| 9 | 29,528 | 229.65 | 30.742 | 0.4671 |
| 10 | 32,808 | 223.15 | 26.436 | 0.4135 |
| 11 | 36,089 | 216.65 | 22.632 | 0.3639 |
| 12 | 39,370 | 216.65 | 19.33 | 0.3108 |
| 15 | 49,213 | 216.65 | 12.045 | 0.1937 |
| 20 | 65,617 | 216.65 | 5.475 | 0.08891 |
| 25 | 82,021 | 221.55 | 2.511 | 0.04008 |
| 30 | 98,425 | 226.55 | 1.172 | 0.01841 |
| 40 | 131,234 | 251.05 | 0.287 | 0.003996 |
| 50 | 164,042 | 270.65 | 0.0798 | 0.001027 |
| 60 | 196,850 | 247.05 | 0.0203 | 0.0003097 |
| 70 | 229,659 | 219.55 | 0.00463 | 8.283E-5 |
| 80 | 262,467 | 198.65 | 0.000886 | 1.846E-5 |
| 86 | 282,152 | 186.85 | 0.000373 | 6.96E-6 |
Guide
How to use this calculator
- Enter the geometric altitude.
- Select meters, kilometers, or feet.
- Use the interpolated standard-atmosphere result for early aerospace, HVAC, fluid mechanics, or thermodynamic checks.
Reference
What the results mean
Air temperature
Air temperature is the thermodynamic temperature of the atmosphere at a given altitude in the standard atmosphere model.
Lapse rate
In the lower atmosphere, ISA temperature decreases at about 6.5 K/km until the tropopause.
Engineering use
Use temperature-altitude values for density estimates, aircraft performance, compressible flow, HVAC derating, and thermal calculations.
Standard atmosphere
ISA temperature is a reference model, not a weather report. Actual temperatures vary with location, season, and weather.
FAQ
Air temperature vs altitude questions
What is standard air temperature at sea level?
Standard sea-level temperature is 288.15 K, or 15 °C.
How fast does air temperature decrease with altitude?
In the ISA troposphere, temperature decreases by about 6.5 K per kilometer up to 11 km.
Is standard atmosphere temperature the same as actual outdoor temperature?
No. ISA temperature is a reference profile; real temperatures depend on weather, latitude, time of day, and season.
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