Calculate dew point — the temperature at which air becomes saturated with moisture — from air temperature and relative humidity.
This calculator uses the Magnus-Tetens approximation, a widely used formula for estimating dew point from temperature and relative humidity: γ = ln(RH/100) + (17.625T)/(243.04+T), then dew point = 243.04γ/(17.625−γ), with T in °C. It's accurate to within about ±0.4°C for typical atmospheric conditions.
Relative humidity depends on temperature — the same amount of moisture in the air gives a different RH% reading depending on how hot it is. Dew point measures actual moisture content directly, so a dew point of 65°F feels muggy whether the air temperature is 70°F or 95°F, while the RH% for that same muggy air would read very differently at each temperature.
No — dew point can equal air temperature (at 100% relative humidity, meaning the air is fully saturated) but never exceed it.
When the air temperature drops to the dew point, the air becomes saturated and excess moisture condenses out — as dew on surfaces, or as fog if it happens throughout a layer of air.
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