Dew Point & Humidity
Everyday & OtherCalculate dew point temperature, relative humidity, and condensation risk from ambient air temperature and relative humidity using the Magnus-Tetens meteorological formula.
Condensation point at 55% RH · Dry & crisp
About this calculator
The dew point is the temperature to which air must be cooled at constant barometric pressure for water vapor to condense into liquid water (dew, fog, or condensation). Unlike relative humidity (which changes with temperature), dew point is an absolute measure of moisture in the air.
Meteorologists and HVAC engineers use dew point to measure summer mugginess (dew points above 65°F/18°C feel humid; above 70°F/21°C feel oppressive) and prevent mold-causing condensation on building surfaces.
How It Works & Formula
Magnus-Tetens formula: γ(T, RH) = (a × T) / (b + T) + ln(RH / 100). Dew Point T_dp = (b × γ) / (a - γ), where empirical constants for water vapor are a = 17.27 and b = 237.7°C.
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