Relative-humidity approximation (RH) calculator

This method estimates RH from actual versus saturated moisture at the same temperature.

Units

\mathrm{RH} = \frac{w_{\text{actual}}}{w_{\text{saturated at same T}}} \times 100

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

\mathrm{RH} = \frac{0.008}{0.016} \times 100 = 50

Symbol	Meaning	Unit
$\mathrm{RH}$	relative humidity	%
$w_{\text{saturated at same T}}$	saturated water-vapor ratio at same temperature	lb/lb
$w_{\text{actual}}$	actual water-vapor mass per dry-air mass	lb/lb

Symbol	Meaning	Unit
$\mathrm{RH}$	relative humidity	%
$w_{\text{saturated at same T}}$	saturated water-vapor ratio at same temperature	kg/kg
$w_{\text{actual}}$	actual water-vapor mass per dry-air mass	kg/kg

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.