Dew Point Calculator

Please provide values to any two fields in the following and click the "Calculate" button to get the third value.

Air Temperature
Dew Point Temperature
Relative Humidity %

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When you wake up early in the morning, and go outside on a sunny day, you will often see water condensed on the flowers and grass around you. That water is called "dew". Dew point is the temperature at which the water vapor in the air under a constant barometric pressure will condense into liquid water. So, the dew point is a water-to-air saturation temperature. It is closely related to the relative humidity. A high relative humidity means the dew point is closer to the current air temperature. Relative humidity of 100% means the dew point is the same as the current temperature.

In the summer, the human body cools down by the evaporation of sweat. High dew point or relative humidity will suppress the evaporation. Therefore, the human body will feel discomfort. On the opposite side, low dew points or relative humidity can cause the skin to crack and become irritated more easily. Normally relatively humidity between 30% and 50% is considered to be a comfort zone. In summer, it means a dew-point temperature of ~60 degrees Fahrenheit (16 degrees Celsius).

At a given barometric pressure but independent of temperature, the dew point indicates the specific humidity of the air. Comparatively, the relative humidity is heavily depending on the temperature. At the same relative humidity value, the amount of water in air is different for different temperature. This is why pilots of airplanes use the dew point to calculate the likelihood of carburetor icing and fog, and to estimate the height of the cloud base.

Devices called dew point meters are used to measure dew point over a wide range of temperatures. These devices consist of a polished metal mirror which is cooled as air is passed over it. The temperature at which dew forms is, by definition, the dew point. Manual devices of this sort can be used to calibrate other types of humidity sensors, and automatic sensors may be used in a control loop with a humidifier or dehumidifier to control the dew point of the air in a building or in a smaller space for a manufacturing process.