Relative Humidity Calculator
Relative humidity is the amount of water vapor in the air expressed as a percentage of the maximum the air could hold at that temperature. It is the number you see on most weather reports and thermostats, and it drives comfort, condensation and mold risk. This calculator derives relative humidity from the air temperature and the dew point, the two quantities a thermometer and a hygrometer or weather station give you most directly. It works by computing the saturation vapor pressure at both temperatures using the Magnus equation and taking their ratio, the standard method used in meteorology. Enter the air temperature and the dew point, choose Celsius or Fahrenheit, and read the relative humidity instantly. This is handy when a data source reports dew point but not humidity, or when you want to sanity check a sensor. All calculations run locally in your browser for private, immediate results.
How to use Relative Humidity Calculator
- Enter the air temperature.
- Enter the dew point temperature.
- Read the relative humidity percentage.
- Note that closer temperature and dew point mean higher humidity.
Frequently asked questions
How does it get humidity from dew point?
It computes the saturation vapor pressure at both the air temperature and the dew point, then takes their ratio to give relative humidity as a percentage.
What does relative humidity actually mean?
It is the amount of water vapor in the air as a percentage of the maximum the air can hold at that temperature, so warmer air can hold more before reaching 100 percent.
What happens when temperature equals dew point?
When the air temperature and dew point are equal the air is saturated, so relative humidity is 100 percent and dew or fog can form.
What is Relative Humidity Calculator?
Relative humidity is the amount of water vapor in the air expressed as a percentage of the maximum the air could hold at that temperature. It is the number you see on most weather reports and thermostats, and it drives comfort, condensation and mold risk.
Is Relative Humidity Calculator free to use?
Yes. Relative Humidity Calculator is completely free, with no sign-up and no usage limits.
Does Relative Humidity Calculator work in a web browser?
Yes. Relative Humidity Calculator runs in any modern web browser. There is nothing to download or install.
Is my data private with Relative Humidity Calculator?
Yes. Relative Humidity Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
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