Dew Point Calculator

About this calculator

This calculator finds the dew point — the temperature air would need to cool to for the water vapor in it to condense into dew or fog — from the current air temperature and relative humidity, using the Magnus formula, a well-established approximation used in meteorology.

A dew point close to the air temperature signals muggy, uncomfortable conditions (since sweat cannot evaporate efficiently) and a rising risk of fog, while a low dew point means dry, comfortable air; it is used by pilots checking fog risk before flights, gardeners and farmers watching for frost or dew formation overnight, and weather-watchers who find dew point a more reliable comfort indicator than humidity percentage alone.