Altitude Temperature
Calculate temperature at any altitude using the ISA model. Free online altitude temperature calculator with results in Celsius, Fahrenheit, and Kelvin for aviation, hiking, and physics.
About This Calculator
The Altitude Temperature Calculator computes the temperature at any altitude using the International Standard Atmosphere (ISA) model. This free online tool is essential for aviation professionals, meteorology students, mountaineers, hikers, and physics enthusiasts who need to understand how temperature changes with elevation.
The ISA model divides the atmosphere into layers with distinct temperature behavior. In the troposphere (0 to 11 km), temperature decreases at a constant lapse rate of 6.5 °C per kilometer as you move away from the Earth's surface heat source. The tropopause (11 to 20 km) maintains a constant temperature of -56.5 °C. In the lower stratosphere (20 to 32 km), temperature begins to increase at approximately 1 °C per kilometer due to ozone absorption of UV radiation.
The calculator provides results in three temperature units — Celsius, Fahrenheit, and Kelvin — and identifies the atmospheric layer along with its characteristic lapse rate. The interactive temperature profile chart visualizes how temperature changes from sea level to your target altitude.
Regional Notes
India: The ISA standard of 15 °C at sea level works well for most calculations. For high-altitude regions like Leh (3,500 m) or the Himalayan trekking routes, use your local base temperature for more accurate estimates. Indian aviation follows ICAO standards based on the ISA model.
United States: Altitudes in feet are commonly used in aviation and mountaineering. At 35,000 feet (typical cruising altitude), the temperature is approximately -56.5 °C. The US Standard Atmosphere (USSA) model is nearly identical to ISA for most practical purposes. For hiking in the Rockies or Sierra Nevada, subtract about 3.56 °F per 1,000 feet of elevation gain.
United Kingdom: The UK Met Office uses the ISA model as a reference for aviation weather. For hiking in the Scottish Highlands or Snowdonia, the 6.5 °C per km lapse rate provides a good estimate, though maritime conditions and weather fronts can cause significant deviations from the standard model.
Frequently Asked Questions
How does altitude affect temperature in the troposphere?
In the troposphere (0 to 11 km altitude), temperature decreases by approximately 6.5 °C for every 1,000 meters (3.56 °F per 1,000 feet) of altitude gain. This is because the troposphere is heated by the Earth's surface, so moving away from the surface results in cooler temperatures.
What is the standard temperature at sea level according to ISA?
According to the International Standard Atmosphere (ISA) model, the standard temperature at mean sea level is 15 °C (59 °F or 288.15 K). This serves as the reference point for calculating temperature at higher altitudes.
Why does temperature sometimes increase with altitude in the stratosphere?
Temperature increases with altitude in the stratosphere (above 20 km) because the ozone layer absorbs ultraviolet (UV) radiation from the Sun. This absorption heats the upper stratosphere, creating an inversion layer where temperature rises by 1 to 2.8 °C per kilometer.
What is the temperature at typical commercial aircraft cruising altitude?
At the typical commercial aircraft cruising altitude of 35,000 feet (10,668 m), the temperature is approximately -56.5 °C (-69.7 °F or 216.65 K), which is the tropopause temperature where the troposphere meets the stratosphere.
How accurate is the ISA model for real-world weather?
The ISA model provides a standardized reference atmosphere based on average conditions at 45° latitude. Actual temperatures can vary significantly due to local weather patterns, seasons, humidity, and geographic location. The model is most accurate for aviation standard calculations and engineering reference but should not replace actual weather data for forecasting.
What are the different layers of Earth's atmosphere and how does temperature change in each?
Earth's atmosphere has five main layers: Troposphere (0-11 km, temperature decreases at -6.5 °C/km), Stratosphere (11-51 km, temperature increases at 1-2.8 °C/km due to ozone absorption), Mesosphere (51-86 km, temperature decreases at -2.8 °C/km), Thermosphere (86-500+ km, temperature increases dramatically), and Exosphere (500+ km, gradual fade into space).
Can I use this calculator for mountaineering and hiking?
Yes, this calculator is useful for estimating temperature at higher elevations for mountaineering and hiking. Simply enter your current temperature at base elevation and the target altitude to estimate the temperature at your destination. Remember that actual conditions may differ due to weather fronts, time of day, and local topography.
What is geopotential altitude and why is it used in the ISA model?
Geopotential altitude accounts for variations in Earth's gravity with height, latitude, and longitude. It is calculated as Z(h) = Φ(h)/g₀, where Φ(h) is geopotential energy at height h and g₀ is gravitational acceleration at mean sea level. The ISA model uses geopotential altitude for accurate atmospheric property calculations, though the difference from geometric altitude is minor for most practical purposes below 10 km.