This relative humidity calculator can estimate the relative humidity, air temperature or dew point temp by taking account of the rest of the two variables from the formula. You can find more on this topic below the tool.

Please input ONLY 2 out of the 3 fields available, in order to find the desired third variable!

Air temperature (T):
Dew point temperature (Td):
Relative humidity (RH):

How does this relative humidity calculator work?

This is a physics calculator that can help you determine either the:

- humidity percentage if you provide the dew point and air temperatures in Celsius (°C), Fahrenheit (°F) or Kelvin (°K);

- dew point temperature by knowing the air temperature and the relative humidity;

- air temperature by considering the relative humidity and the dew point temperature.

The algorithm behind this relative humidity calculator is based on the formulas explained here:

  • In order to calculate the percentage of the relative humidity the formula applicable is:

RH = 100*((112-0.1*AT+DP)/(112+0.9*AT))

  • To find the dew point temperature the corresponding formula is:

Td = ((RH/100)^(1/8)*(112+0.9*AT) )+(0.1*AT)-112

  • To calculate the air temperature the equation used is:

T = (DP-(112*(RH/100)^(1/8))+112)/((0.9*(RH/100)^(1/8))+ 0.1)


Td = dew point temperature expressed in Celsius (°C).

T = air temperature considered to be in Celsius (°C).

RH = relative humidity in percent (%).

The temperature (air or dew point) can be specified in Celsius (°C), Fahrenheit (°F) or Kelvin (°K). This calculator uses the following temperature conversion rules:

1 °C = 33.8 °F

1 °C = 274.15 °K

Source: Martin Wanielista, Robert Kersten & Ron Eaglin, 1997 - Hydrology Water Quantity and Quality Control. John Wiley & Sons - Second edition.

Understanding the concept of dew point

In physics, the dew point refers to the temperature at which the water vapor from an air sample being exposed to a constant pressure condenses into liquid water at the same rate as the water vaporization rate.

This concept is used to express how much water vapor is in the air at a specific moment, thus the higher the dew point is, the more humid the air is perceived. It comes in the form of an absolute value measured by specialized dew point meters over various levels of temperatures and it is often used in industries that require calibration of humidity sensors.

21 May, 2015