How to Calculate Dew Point

When the dew point is reached, humidity in the air becomes liquid water.
••• Dew image by photorich from

According to the International Research Institute for Climate and Society at Columbia University, dew point is defined as "...the temperature to which the air must be cooled at constant pressure in order for it to become saturated, i.e., the relative humidity becomes 100 percent." What that means, in simple terms, is that the dew point is the temperature at which the moisture in the air becomes liquid water. It is a complicated calculation to determine the dew point, but according to Mark G. Lawerence in a 2005 paper published through the American Meteorological Society, there is a relatively simple approximation that can be used.

    Subtract the relative humidity from 100.

    Divide that answer by 5 and jot down your result.

    Subtract the answer that you jotted down from the current temperature in degrees Celsius. The result is a reasonable approximation of the dew point in degrees Celsius.

    Things You'll Need

    • Scratch paper
    • Pencil


    • There are online dew point calculators that will calculate dew point for you. See the Resources section.


    • Keep in mind that this procedure is an approximation, albeit a good one.

      Be sure that the temperature you use is in Celsius.

Related Articles

The Relationship Between Moisture & Temperature
How to Understand Barometric Pressure Readings
How to Find the X Intercept of a Function
How to Find the Vertical Tangent
How to Find the Slope in a Circle
Characteristics of Aquatic Plants
How to Calculate CV Values
How to Calculate the Coefficient of Variation
How to Calculate Relative Accuracy
How to Convert hPa to Altitude
The Effects of Temperature on the pH of Water
How to Find a Z Score
How to Divide Rational Numbers
How to Interpret a Student's T-Test Results
How to Calculate Rain to Snow
How Does Water Enter the Earth's Atmosphere?
How to Make a Homemade Weather Vane for Kids
How to Explain Relative Humidity to Children
How to Calculate Antipode
How to Calculate the Area of a Curved Surface

Dont Go!

We Have More Great Sciencing Articles!