💧 Dew Point Calculator
The dew point is the temperature at which air becomes saturated and water starts condensing out — it is the most honest measure of how muggy the air feels. This calculator derives it from temperature and relative humidity using the Magnus formula.
A dew point under 55°F feels dry and comfortable, 60–65°F feels muggy, and anything above 70°F feels oppressive. Pilots, painters and runners all watch it closely.
How to use this calculator
Enter the air temperature in Fahrenheit and the relative humidity percentage. The calculator applies the Magnus formula and returns the dew point in Fahrenheit and Celsius.
- Type the Air temperature in Fahrenheit.
- Type the Relative humidity as a percentage.
- Read the dew point result instantly.
- Compare it against the comfort guide: under 55 feels dry, over 70 feels oppressive.
Frequently asked questions
What does the Dew Point Calculator compute?
It finds the temperature at which the air becomes saturated and water begins condensing, using the Magnus formula on your temperature and humidity inputs. It reports the result in both Fahrenheit and Celsius.
What is the Magnus formula?
With constants a = 17.27 and b = 237.7, an intermediate value alpha equals a times T over (b plus T), plus the natural log of relative humidity over 100, where T is in Celsius. The dew point is then b times alpha over (a minus alpha).
Can you give a worked example?
At 77 degrees Fahrenheit and 50 percent humidity the dew point is 56.9 degrees Fahrenheit, or 13.8 Celsius, which feels fairly comfortable.
How do I read the result?
A dew point under 55 degrees Fahrenheit feels dry, 55 to 60 is comfortable, 60 to 65 feels muggy, and above 70 feels oppressive. The gap between air temperature and dew point also hints at fog risk when it narrows near the ground temperature.