💧Dew Point Calculator

About this tool

Enter the air temperature and relative humidity (in °C or °F) to get the dew point, or switch modes to find relative humidity from a dew point. You also get absolute humidity, the humidex 'feels like' temperature, the temperature–dew point spread, the frost point below freezing and a comfort rating.

Why the dew point matters

The dew point is the temperature to which air must cool for its water vapour to condense into dew, fog or condensation on a cold window. Relative humidity swings up and down as the air warms and cools during the day, but the dew point stays the same unless moisture is added or removed, so it's a better measure of how humid the air really is and how sticky it feels. As a guide, a dew point below about 10 °C feels dry, 13–16 °C comfortable, 18–21 °C muggy and above 24 °C oppressive. At 25 °C and 60% relative humidity the dew point is 16.7 °C. This tool uses the Magnus formula, accurate to a fraction of a degree in everyday conditions, and also reports absolute humidity (13.8 g of water per cubic metre in that example), the Canadian humidex and the gap between air temperature and dew point. Fog and low cloud form as that gap nears zero, and condensation appears on any surface colder than the dew point, which is why it matters for damp and mould at home. Honest limits: humidex is one of several heat indices; for heat warnings follow your weather service. The feels-like temperature calculator and the air density calculator are related.

Frequently asked questions