Dew Point Calculator
Turn temperature and relative humidity into the dew point — the truest measure of how muggy the air actually feels.
Dew point is the temperature air would need to cool to for dew to form. It’s a better gauge of muggy-ness than humidity alone: once it climbs past 65°F (18°C), most people start to feel the air get sticky.
How it works
The dew point is the temperature the air would have to cool to before the water vapor in it starts condensing into dew, fog, or clouds. The closer the dew point is to the current temperature, the more moisture is packed into the air.
This tool uses the Magnus formula with the standard constants a = 17.27 and b = 237.7°C. Give it the air temperature and the relative humidity, and it solves for the dew point. It also tags the result with a plain-language comfort level.
Meteorologists like the dew point because, unlike relative humidity, it doesn't swing around as the temperature changes through the day. A dew point in the 40s feels crisp; once it climbs past 65°F (18°C), most people describe the air as sticky.
Frequently asked questions
Dew point vs. relative humidity — what's the difference?
Relative humidity is a percentage that depends on temperature, so it rises and falls all day even when the moisture doesn't change. Dew point is an actual temperature that tracks the raw amount of water in the air, making it a steadier comfort gauge.
What dew point counts as comfortable?
Below about 55°F (13°C) the air feels dry and pleasant. From 60 to 65°F it starts to feel sticky, and above 70°F (21°C) it's oppressive — the range where summer nights feel like you can't cool off.
Can the dew point be higher than the temperature?
No. The dew point can at most equal the air temperature, and when they match the humidity is 100% and dew or fog forms. If your inputs would push it higher, something's off with the numbers.