Dew Point Calculator

The dew point is the temperature at which air becomes saturated and dew forms.

How the Math Works

The Dew Point Calculator uses the Magnus formula approximation to estimate the temperature at which air becomes saturated with water vapor. This formula relates temperature, relative humidity, and dew point through a logarithmic relationship: it calculates the actual vapor pressure using relative humidity and temperature, then applies the Magnus equation to solve for the dew point temperature. The approximation uses empirically derived constants that make the calculation both accurate and computationally efficient for everyday use.

Practical Applications

To use this calculator, simply input the current air temperature and relative humidity readings from a weather station or home weather instrument. The temperature should be in degrees Celsius or Fahrenheit (the calculator handles conversion), and humidity should be expressed as a percentage. After entering these values, press the calculate button to instantly receive the dew point temperature, which represents the temperature at which condensation would begin forming if the air were to cool further at constant pressure.

Day-to-Day Use

Knowing your dew point helps you understand how comfortable the air will feel - when dew point and temperature are close, the air feels muggy because sweat can't evaporate efficiently from your skin. This information is valuable for planning outdoor activities, deciding when to use air conditioning, or determining if your clothes will stay damp after exercising. It's also useful for gardeners who need to understand moisture conditions, or anyone curious about why certain days feel oppressively humid while others feel dry despite similar temperatures.

Worked example

25 °C, 60% RH → ~16.7 °C.

FAQ