Dew Point Calculator
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Dew Point Temperature
0.0 °C
Comfort Level
What is Dew Point?
The dew point is the temperature at which air becomes saturated with water vapor, causing condensation to form. When the air temperature cools to the dew point, the relative humidity becomes 100%, and dew, fog, or clouds begin to form.
Understanding Dew Point and Comfort
The dew point is directly related to how comfortable you feel in the air. Unlike relative humidity, which changes with temperature, the dew point is an absolute measure of moisture in the air.
| Dew Point (°F) | Dew Point (°C) | Comfort Level |
|---|---|---|
| Less than 50°F | Less than 10°C | Dry and comfortable |
| 50-59°F | 10-15°C | Comfortable |
| 60-64°F | 15-18°C | Somewhat comfortable |
| 65-69°F | 18-21°C | Somewhat uncomfortable |
| 70-74°F | 21-24°C | Very humid, quite uncomfortable |
| 75°F or higher | 24°C or higher | Extremely uncomfortable, oppressive |
Dew Point vs. Relative Humidity
While relative humidity measures the percentage of moisture in the air compared to what the air can hold at a specific temperature, dew point is an absolute measurement of moisture. This makes dew point a better indicator of comfort than relative humidity.
For example, a 90°F day with 70% relative humidity has a dew point of about 78°F, which feels extremely uncomfortable. However, a 70°F day with 70% relative humidity has a dew point of about 60°F, which feels much more comfortable.
How to Use the Dew Point Calculator
To use the calculator:
- Enter the current air temperature
- Select the temperature unit (Celsius or Fahrenheit)
- Enter the relative humidity percentage
- The calculator will automatically compute the dew point temperature and comfort level
- You can also view a chart showing how dew point changes with humidity at the current temperature
Dew Point Formula
The formula used to calculate the dew point is:
Td = T - ((100 - RH)/5)
Where:
- Td = Dew point temperature
- T = Current air temperature
- RH = Relative humidity (%)
This is a simplified approximation. For more accurate calculations, the calculator uses the Magnus-Tetens formula:
Td = (b × α(T,RH)) / (a - α(T,RH))
Where:
- α(T,RH) = ln(RH/100) + (a × T)/(b + T)
- a = 17.27
- b = 237.7°C
Applications of Dew Point
Understanding dew point is important for:
- Weather forecasting and predicting fog or dew formation
- HVAC system design and operation
- Indoor climate control and comfort
- Agriculture and frost prediction
- Industrial processes where moisture control is critical
- Outdoor activities planning