Dew point calculator
Calculate the dew point from the air temperature and relative humidity.
The dew point is the temperature at which the air saturates and vapor starts to condense. Higher means muggier.
How the calculation works
The dew point is the temperature at which air becomes saturated with vapor and starts to condense (dew, mist, fogged glass). We use the Magnus-Tetens formula from temperature and relative humidity.
The higher the dew point, the muggier the air — because it holds more water vapor.
Comfort ranges
- Up to ~15 °C: pleasant and dry.
- 16 to 20 °C: getting uncomfortable.
- Above 21 °C: muggy, sticky.
Examples
- 30 °C at 60% humidity: dew point ~21 °C (muggy).
- 20 °C at 40% humidity: dew point ~6 °C (dry and pleasant).
Frequently asked questions
Dew point or humidity?
Dew point describes "mugginess" better than relative humidity alone.
Why does the car window fog up?
When the glass surface drops below the air's dew point, vapor condenses on it. Warming the glass or lowering humidity clears it.
Can the dew point exceed the temperature?
No. At most it equals the air temperature — that is 100% humidity, when mist forms.
Dew point versus relative humidity?
Dew point measures the absolute water vapour in the air; relative humidity measures how full the air is for that temperature. Dew point describes discomfort far better.
Why does a cold glass sweat?
Because the cold surface cools nearby air to its dew point and vapour condenses. The water comes from the air, not the glass.
Does dew point predict frost?
Yes. With a dew point below 0 °C, vapour deposits directly as ice on cold surfaces, forming frost.
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See all →Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources