# Relative Humidity

on . Posted in Fluid Dynamics

Relative humidity, abbreviated as RH, a dimensionless number, is a measure of the amount of moisture in the air with respect to the temperature.

## Relative Humidity formula

$$\large{ RH = \frac{e}{e_s} \;100 }$$
Symbol English Metric
$$\large{ RH }$$ = relative humidity  $$\large{dimensionless}$$
$$\large{ e }$$ = actual vapor pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$
$$\large{ e_s }$$ = saturated vapor pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$

## Relative Humidity formula

$$\large{ RH = 100 \; \left( \frac{ 112 \; - \; 0.1 \; T \; + T_d }{ 112 \; + \; 0.9 \; T } \right)^8 }$$
Symbol English Metric
$$\large{ RH }$$ = relative humidity  $$\large{dimensionless}$$
$$\large{ T_d }$$ = dewpoint $$\large{F}$$ $$\large{C}$$
$$\large{ T }$$ = temperature $$\large{F}$$ $$\large{C}$$