Relative humidity is the ratio of actual mass of vapor content in the air for a given volume and temperature to that required to make the air saturated with vapor at that temperature.
% Relative humidity =(actual mass of water vapor content in the air in a given volume / mass of vapor needed to make the air saturated in that volume) x 100
The relative humidity at the dew point is 100%. If the relative humidity is more than
60% the air is humid or if the relative humidity is less than 60%, the air is dry.