Dew point has always been difficult to calculate. Namely, the dew point is a temperature at which moisture in the air starts to condensate on the surface (forming dew). This is a classic gas to liquid conversion.
To simplify how to calculate the dew point, we are going to look at the dew point formula, simple-to-use calculator, and chart of dew points at different temperatures and humidity levels.
The calculated dew point always depends on relative humidity levels (RH). The higher humidity we have, the higher the dew point temperature will be.
Example: At 80°F temperature and 60% humidity levels the dew point is 66°F. That means that above 66°F, we won’t see any condensation (dew formation). At 66°F and below (let’s say 60°F, 50°F, and so on), we will see water condensation. For comparison, at higher 80% humidity levels, the dew point is higher (73°F, to be exact).
The real question is this:
How do you calculate dew points at different temperatures and relative humidity levels?
It’s quite straightforward (but not all that simple). You just use this dew point formula:
This dew point equation is quite complex. Usually, only we physicists and other scientists use it. Luckily, there is a much simple formula everybody can use to calculate dew point.
To help out everybody looking to figure out dew point temperatures, we have prepared 3 sections on dew points:
- Dew Point Formula. To calculate the dew point manually, you will have to use the dew point temperature formula. Instead of using this complex formula, we can use a simplified dew point calculation formula, introduced by Mark G. Lawrence in the Bulletin of the American Meteorological Society in 2005. We will look at this first.
- Dew Point Calculator. This is a calculator that automatically calculates dew point; you just have to input temperature and relative humidity. You can play around with numbers to see how the dew point temperature varies based on the inputs.
- Dew Point Chart + Dew Point Comfort Chart. If you’re looking for a dew point, you can simply consult a dew point chart. This includes dew point temperatures at different temperatures and relative humidity levels. On top of that, we have also included a ‘Comfort Chart’ that tells you how humans feel at different dew point temperatures. Example: At 61°F To 65°F dew point temperature, we start to ‘get sticky’. Dew points between 71°F To 75°F are labeled as ‘Oppressive’.
Let’s look at the formula first to see how the dew point is calculated. After that, you can use the dew point calculator yourself, and consult the charts as well:
Dew Point Formula (Simplified Version)
As we know, the dew point is calculated from relative humidity (RH) and air temperature (T). The dew point calculation formula, as we have seen, is quite complex.
That’s why Mark G. Lawrence introduced a simple way how to calculate dew point in the 2005 article titled ‘The Relationship between Relative Humidity and the Dewpoint Temperature in Moist Air: A Simple Conversion and Applications’, published in the Bulletin of the American Meteorological Society.
This is a simple dew point temperature formula everybody can use:
The RH is the equation that stands for ‘Relative Humidity’, T is air temperature (expressed in °C, not in °F), and we are calculating Tdew also in °C.
This dew point equation adequately determines dew point temperature. At humidity levels of 50% or more, the discrepancy from the actual dew point (calculated by the complex equation) is less than 1 degree.
Let’s look at an example of how to use the dew point formula. After this, you can use the dew point temperature calculator that does all this automatically.
Example: Let’s say we want to calculate the dew point at 95°F (35°C) and 70% relative humidity. You just insert the temperature (in °C) and RH in the equation, and you will get the dew point temperature (in °C) like this:
Tdew = 35°C – ((100 – 70)/5) = 29°C
Of course, if you want to get the dew point is degrees of Fahrenheit, you will have to convert °C to °F. 29°C, for example, is equal to 84.2°F. That means that a dew point at 95°F and 70% relative humidity is 84.2°F.
Note: You can also see that at 100% humidity levels, the dew point temperature is the same as the air temperature. T = 95°F and Tdew = 95°F as well.
To avoid all these temperature unit conversions and simplify the whole process, you can use the dew point calculation that does all of this automatically:
Dew Point Calculator (Insert Temperature And Relative Humidity; Get Dew Point Temperature)
This calculator is fairly simple to use. You just have to insert air temperature (in °F) and relative humidity, and you will get the dew point temperature (in °F). You can play around with numbers (just slide the temperature or/and humidity slider in a left-right direction and see how the dew point temperature changes).
Note: If you would like us to create a similar dew point calculator in degrees Celsius, just give us a hint in the comments, and we’ll take some time to make it.
For example, you can check what is the dew point temperature at 90°F air temperature and 75% relative humidity. Use the slider and you should get this correct result:
On top of that, you can also consult the dew point temperature chart below (using this calculator, we can create the dew point calculator chart). What is really interesting to see is the dew point comfort chart as well; this will tell you how we feel at certain dew point temperatures.
Dew Point Chart (Temperature And Relative Humidity Chart)
The dew point chart tells you what a dew point temperature is at a certain temperature and at certain relative humidity. This chart is also referred to as the ‘dew point temperature chart’ or the ‘dew point humidity chart’ since it includes both T and RH.
|RH/T:||50% RH||55% RH||60% RH||65% RH||70% RH||75% RH||80% RH||85% RH||90% RH||95% RH||100% RH|
You can just check what the dew point is at any T or H.
Example: What is the dew point temperature at 120°F and 90% humidity? From the dew point chart, you can quickly see that the dew point temperature at these conditions is 116°F.
Let’s finally look at what all these dew point temperatures mean:
Dew Point Comfort Chart
At what dew point temperature do we start to feel uncomfortable?
The dew point comfort chart tells us how we, as humans, experience different dew point temperatures. Namely, at 66°F dew point, we start to feel uncomfortable:
|Dew Point Temperature (°F):||Comfort Levels:|
|55°F And Below||Pleasant|
|56°F To 60°F||Comfortable|
|61°F To 65°F||Getting Sticky|
|66°F To 70°F||Uncomfortable|
|71°F To 75°F||Oppressive|
|76°F And Above||Miserable|
Here is important to notice that dew point temperatures takes into account both:
- Air temperature.
- Relative humidity.
For example, 66°F dew point or higher is designated as ‘Uncomfortable’. This is usually meant as an 80°F air temperature and 60% humidity levels situation.
With all these resources, we hope you will now be able to adequately determine the dew point temperature. If you have any questions, you can use the comment section below and we’ll try to help you out.
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