Standard Atmosphere Calculator

About the Standard Atmosphere Calculator

The International Standard Atmosphere models how temperature and pressure fall with altitude in the troposphere (up to ~11 km), with a lapse rate of 6.5 °C/km from a 15 °C, 1013.25 hPa sea-level datum.

How to use

Enter an altitude in metres (0 to 11000), then click Calculate.

Worked example

At 1500 m → about 5.25 °C and 845 hPa.

How to use this calculator

1. Enter the altitude you want to evaluate.
2. Choose the troposphere ISA model if the tool offers model options.
3. Read the calculated temperature and pressure instantly.
4. Compare the result with sea level values to understand the change with height.

The formula explained

• \(T_0\) = sea level standard temperature
• \(P_0\) = sea level standard pressure
• \(L\) = temperature lapse rate in the troposphere
• \(h\) = altitude above sea level
• \(g\) = standard gravitational acceleration
• \(M\) = molar mass of air
• \(R\) = universal gas constant
• \(\text{Temperature}\) = air temperature at the given altitude
• \(\text{Pressure}\) = air pressure at the given altitude

Step by step method

1. Start with the altitude above sea level in meters or feet, depending on the tool's input format.
2. The calculator applies the ISA troposphere formula to estimate temperature drop and pressure decrease with height.
3. It computes the values using standard atmosphere constants, so the result reflects an idealized standard day.
4. Use the output as a reference for aviation, engineering, or weather-related calculations, not as a live weather report.

Worked example

Suppose you want the standard atmosphere conditions at 2,000 meters altitude.

1. Use the ISA troposphere temperature relation \(T = 15 - 0.0065 \times 2000\). This gives \(T = 15 - 13 = 2\) degrees Celsius.
2. For pressure, the troposphere formula gives a value of about 79.5 kPa at 2,000 meters under standard conditions.
3. These are ideal standard-atmosphere values, not measured weather values.

Tips and common mistakes

• This calculator uses the ISA troposphere model, so it is best for altitudes in the lower atmosphere.
• Do not confuse standard atmosphere values with actual weather, which can differ a lot from the model.
• Check the altitude units carefully, because a unit mix-up can change the result dramatically.
• If you need conditions above the troposphere, use a model that supports higher atmospheric layers.

Frequently asked questions