Power Calculators

💧 Dew Point Calculator

Calculate dew point temperature from air temperature and relative humidity using a standard Magnus-type meteorological equation.

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Enter details

Enter the current air temperature.
Enter relative humidity from 0 to 100 percent.

Fill in the details and click Calculate to see your results.


Also available in our Android app, with charts and full breakdown tables.

📘 About the Dew Point

Dew point is a measure of atmospheric moisture.

It is the temperature at which air becomes saturated when cooled without changing its water-vapor content.

When the air temperature and dew point are close together, the relative humidity is high.

Dew point is often more useful than relative humidity for describing how much moisture is actually present in the air.

✏️ Worked examples

Example 1 - 30°C and 70% RH

You enter
Air Temperature30
Temperature UnitCelsius (°C)
Relative Humidity70%
You get
Dew Point (°C)23.9366
Dew Point (°F)75.0859
Dew Point Depression (°C)6.06339
Dew Point Depression (°F)10.9141
Humidity Input Valid (1 = Yes, 0 = No)1

At 30°C and 70% relative humidity, the calculated dew point is approximately 23.9°C.

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Example 2 - 20°C and 50% RH

You enter
Air Temperature20
Temperature UnitCelsius (°C)
Relative Humidity50%
You get
Dew Point (°C)9.27009
Dew Point (°F)48.6862
Dew Point Depression (°C)10.7299
Dew Point Depression (°F)19.3138
Humidity Input Valid (1 = Yes, 0 = No)1

At 20°C and 50% relative humidity, the dew point is approximately 9.3°C.

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Example 3 - Saturated air

You enter
Air Temperature25
Temperature UnitCelsius (°C)
Relative Humidity100%
You get
Dew Point (°C)25
Dew Point (°F)77
Dew Point Depression (°C)0
Dew Point Depression (°F)0
Humidity Input Valid (1 = Yes, 0 = No)1

When relative humidity is 100%, the dew point approaches the air temperature.

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🧭 How to use this calculator

What you enter

  • Air TemperatureEnter the current air temperature.
  • Temperature Unit
  • Relative Humidity (%)Enter relative humidity from 0 to 100 percent.

What you get

  • Dew Point (°C)
  • Dew Point (°F)
  • Dew Point Depression (°C)
  • Dew Point Depression (°F)
  • Humidity Input Valid (1 = Yes, 0 = No)

💡 What is dew point

  • Dew point is the temperature at which air reaches saturation.
  • At the dew point, relative humidity is 100 percent.
  • If air is cooled below its dew point, water vapor can condense into liquid water or deposit as ice depending on conditions.

💡 Dew point versus relative humidity

  • Relative humidity depends on both moisture content and temperature.
  • Dew point is more directly related to the amount of water vapor present.
  • A warm day can have a high dew point even when relative humidity is not especially high.

💡 Dew point depression

  • Dew point depression is air temperature minus dew point temperature.
  • A small depression indicates air close to saturation.
  • A large depression generally indicates drier air.

❓ Frequently asked questions

What is dew point?

Dew point is the temperature to which air must be cooled for saturation to occur while its water-vapor content remains approximately unchanged.

How is dew point calculated?

This calculator uses a Magnus-type saturation vapor pressure relationship involving air temperature and relative humidity.

What does a high dew point mean?

A higher dew point generally indicates more water vapor in the air and often corresponds to muggy conditions when temperatures are warm.

What happens when temperature equals dew point?

Relative humidity is approximately 100 percent and condensation can occur if additional cooling occurs.

Can dew point be higher than air temperature?

Under physically consistent measurements, dew point should not exceed the air temperature.

Is dew point better than humidity for describing moisture?

Dew point is often more intuitive because it directly indicates atmospheric moisture content, whereas relative humidity changes with temperature.