About this Dew Point
Relative humidity can be misleading. The same humidity percentage can feel mild on a cool day and oppressive on a warm one. Dew Point is the absolute measure of how much moisture is in the air. It is the temperature at which dew forms, and this calculator shows the result in Celsius.
Who this calculator is for
- Weather watchers comparing comfort across different days.
- Homeowners, gardeners, and outdoor planners tracking muggy conditions.
- Anyone who wants a better humidity measure than relative humidity alone.
When to use it
- Estimate how muggy or comfortable the air feels.
- Compare dew point readings between different forecast days.
- Check whether the air is close to saturation and condensation.
How to use this calculator
- Enter the Air Temperature.
- Enter the Relative Humidity.
- The result is the Dew Point temperature.
Key assumptions
- Temperature is entered in Celsius and humidity is relative humidity.
- The dew point is calculated from the Magnus approximation.
- Dew point cannot exceed the air temperature.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
This calculator uses the Magnus Formula approximation to solve for Dew Point ($T_d$) given Temperature ($T$) and Relative Humidity ($RH$).
Inputs explained
Relative Humidity
The percentage of water vapor in the air relative to the maximum capacity at that temperature.
Understanding your results
* < 12°C: Dry and comfortable.
* 12-16°C: Pleasant.
* 16-21°C: Humid / Sticky.
* 21-24°C: Oppressive / Uncomfortable.
* > 24°C: Severe / Miserable.
Example scenarios
Comfortable
Temp 25°C, Humidity 30%. Dew Point 7°C. Feels dry and comfortable.
Oppressive
Temp 30°C, Humidity 80%. Dew Point 26°C. Feels very muggy.
Key Features
- Magnus Formula
- Comfort Level Indicator
- Celsius Input (Standard)
Tips & Best Practices
- Dew Point can never be higher than the air temperature.
- When the Dew Point equals the air temperature, humidity is 100% (Saturation), and fog or rain usually forms.
Glossary of Terms
- Saturation
- The state when air holds the maximum amount of water vapor possible at that temperature.
- Condensation
- The conversion of vapor to liquid. Happens on cold drinks when the surface temp is below the dew point.