Low Light Leaf Dew Point Calculator

Low Light Leaf Dew Point Calculator converts room temperature and relative humidity into the dew point, the temperature at which water starts to condense on surfaces. Enter your room temperature and humidity reading, and the tool shows you the dew point in Fahrenheit or Celsius. At 70°F and 40% humidity, for example, the dew point is about 45°F, so any window glass colder than that will fog or drip.

You can also measure the inside surface temperature of your window glass with an infrared thermometer and add it to the calculator to see whether that specific pane will fog at your current humidity. The result tells you the maximum humidity your coldest window can tolerate before it gets wet. A reference chart shows dew points across common indoor temperatures and humidity levels from 20% to 70% relative humidity.

The calculator uses the Magnus approximation with Alduchov and Eskridge constants, the same equations published by the University of Miami. It runs in your browser and is free to use, link to or cite.