Dew Point Calculator Online

People use the Dew Point Calculator as a tool to determine the temperature at which dew will form, given a specific relative humidity (RH) expressed as a percentage. This temperature, known as the dew point temperature, is a key factor in assessing atmospheric moisture and potential condensation.

Formula of Dew Point Calculator

The formula used for calculating the Dew Point Temperature (°C) is as follows:

Dew Point Temperature (°C) = (B * ln(RH/100)) / (A – ln(RH/100))

Where:

• Dew Point Temperature (°C) is the temperature at which dew will form.
• RH is the relative humidity expressed as a percentage.
• A and B are constants specific to the units being used (either °C or °F).

For temperatures in degrees Celsius (°C), the values of A and B are approximately:

• A = 17.27
• B = 237.7

For temperatures in degrees Fahrenheit (°F), the values of A and B are approximately:

• A = 17.27
• B = 41.5

How to Use the Formula:

1. Measure the relative humidity (RH) as a percentage.
2. Plug the values of A, B, and RH into the formula.
3. Calculate the dew point temperature in either °C or °F, depending on your preference.

For example, if RH is 60% and you’re using the Celsius version of the formula:

Dew Point Temperature (°C) = (17.27 * ln(60/100)) / (17.27 – ln(60/100))

Example of Dew Point Calculator

Let’s illustrate the practical application of the Calculator with an example:

Suppose you have a relative humidity (RH) reading of 75% and you want to find the dew point temperature in degrees Fahrenheit (°F).

Using the formula for temperatures in °F:

Dew Point Temperature (°F) = (41.5 * ln(75/100)) / (17.27 – ln(75/100))

Calculating this, you would find the dew point temperature in °F.

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