Dew Point Calculator

The dew point is the temperature to which air must cool for water vapor to condense into dew, fog, or clouds. It is a direct measure of how much moisture is actually in the air. Unlike relative humidity, the dew point does not change as the air temperature rises and falls during the day.

This calculator uses the Magnus formula with the Alduchov-Eskridge coefficients (a = 17.625, b = 243.04°C). It combines the air temperature and relative humidity to solve for the saturation temperature. The result is accurate to a few tenths of a degree across normal weather conditions.

A dew point below 55°F (13°C) feels comfortable and dry. From 55–60°F it starts to feel sticky, 60–65°F is noticeably humid, 65–70°F is muggy and uncomfortable, and above 70°F (21°C) is oppressive. Dew points above 75°F are rare and can be dangerous for outdoor activity.

Relative humidity is the percentage of moisture the air holds relative to its maximum at the current temperature, so it swings widely as the temperature changes. Dew point is the absolute moisture content and stays steady. That is why meteorologists prefer dew point to describe how humid it really feels.

No. The dew point can equal the air temperature — which happens at 100% relative humidity, when fog or dew forms — but it can never exceed it. As the two values converge, the air is fully saturated and condensation begins.