HVAC - Dew Point Approximation

Dew point of moist air from ambient temperature and relative humidity using Magnus formula - the basis for condensation check.

Dew pointHVACPsychrometrics

Air temperature°CRelative humidity%

Dew-point temperature: 19.1°C

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

T_d = \frac{b \cdot \alpha}{a - \alpha}, \quad \alpha = \ln(\text{RH}/100) + \frac{a T}{b + T}

Symbol	Meaning	Unit
$RH$	Relative humidity	%
$T$	Air temperature	°C

Source: ASHRAE Fundamentals Ch. 1

In short

Dew point of moist air from ambient temperature and relative humidity using Magnus formula - the basis for condensation check.

Learn the theory Marine Auxiliary Engines and Generators