Dew Point Calculator

Calculate the dew point based on temperature and relative humidity, for free with this calculator.

Required Information

Result:

What it is

What is Dew Point?

Create Date: July 17, 2024

Last Modified Date: November 18, 2024

Dew point is the temperature that the air must reach for it to be completely saturated with water, effectively making it 100% humid. At this point, it will likely rain or become very foggy.

How to Calculate Dew Point

Calculating dew point can be done with the following equation that is called the Magnus formula:

An image showing the formula for calculating the dew point.
Where:
  • DP = Dew Point

  • α(T, RH) = a × (T / (b + T)) + ln(RH / 100)

  • a = 17.27

  • b = 237.7

  • RH = Relative Humidity

Understanding Your Results

Your result will be a single value, the temperature at which the air will be completely saturated with water. This value is displayed in Fahrenheit by default, but can be converted easily into Celsius or Kelvin by choosing them from the dropdown menu.

How to Use the Dew Point Calculator

  1. Enter the temperature, as well as changing the measurement type to the correct unit.

  2. Enter the humidity percentage. Do not enter the percent symbol, the number itself is all that is needed. For example, just entering 5 will do the job.

  3. Hit calculate and get your results instantly!

Example Calculation

Let's say it is 40 degrees Fahrenheit outside and the current relative humidity is 58%. We can plug those values into this tool to get the dew point temperature. First we enter 40 into the temperature field and then 58 into the humidity field.

We can now hit calculate to get the dew point temperature of 26.43 degrees Fahrenheit, or -3.09 degrees Celsius.

Dew Point - Frequently Asked Questions

Dew point is the temperature at which the air becomes saturated with water vapor whereas humidity is the percent of the air that is currently full of water. If it is more humid, it means the air is holding onto more water, which can make it feel muggy and sticky. Low humidity makes it feel very dry out.

Yes, there is a chance that dew point can be a temperature that is lower than 0.

The highest dew point ever recorded was 95°F in Saudi Arabia, back in 2003 where it was 108°F at the time.

Similar Tools

Related Calculators

We have hundreds of calculator tools for you to use for free. Here are a few similar tools that you should check out next.