BROWSE HOW TOs

How to Compute the Dewpoint

By eHow Home & Garden Editor

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Knowing how to compute the dew point is an important part of becoming a good amateur meteorologist. Knowing the dew point will let you know if dew might form at certain times as the temperature goes up and down through the course of a day. Computing the dew point is fairly simple if you use the following formula.

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Instructions

Difficulty: Moderately Easy

Step1

Find the temperature outside. There are several pieces of information that you need in order to accurately compute the dew point. Temperature is one of the most important bits of information that you need. Depending on the formula that you use, you need to determine the temperature in a particular type of degrees, such as Kelvin, Fahrenheit or Celsius. For this formula, you will need to use the temperature in Celsius.

Step2

Determine the relative humidity (RH). Be sure to use the relative humidity as a fraction rather than as a percentage.

Step3

Use the following equation: Td = T – ((100 – RH)/5).

Step4

Insert the temperature in the place held by T.

Step5

Insert the relative humidity in the place held by RH.

Step6

Calculate the dew point by completing the equation. This can be used as long as the relative humidity is 50 percent or more. The formula for determining the dew point is more complicated when the relative humidity is less than 50 percent.