Dew Point Calculator
Estimate dew point, temperature spread and vapor pressure from temperature and humidity.
What would you like to do next?
Convert temperature and relative humidity into dew point
Enter air temperature in Celsius or Fahrenheit and a relative humidity percentage. The calculator converts to Celsius internally, uses a Magnus saturation-vapor-pressure approximation over liquid water and returns dew point, temperature-dew point spread and actual vapor pressure. Results are converted back to the selected temperature unit while the pressure remains visible in hectopascals.
Recognize the limits of an approximation
Dew point describes saturation for the entered air parcel and is not itself a forecast of rain, fog or condensation on every surface. Sensor accuracy, rapid changes, ice-phase conditions and temperatures outside the formula range can change the result. Use current calibrated observations and official weather information when conditions matter.
Frequently asked questions
What does dew point represent?
It is the temperature at which the entered air parcel reaches saturation under the stated assumptions.
Can I enter Fahrenheit?
Yes. The calculator converts internally and returns the dew point in the selected unit.
Does a close spread guarantee fog?
No. Mixing, terrain, wind and the vertical profile also affect cloud and fog formation.