Relative Humidity

Not Reviewed
Equation / Last modified by KurtHeckman on 2018/07/10 16:18
Anastase.Relative Humidity

The Relative Humidity calculator computes the relative humidity based on the actual density of vapor and the saturated density.

INSTRUCTIONS: Choose units and enter the following:

  • (W) This is the actual density of vapor
  • (Ws)  This is the saturation density.

Relative Humidity(rh): The calculator returns the relative humidity as a percentage.

The Math / Science

Relative humidity is the amount of moisture in the air compared to what the air can "hold" at that temperature.  Relative Humidity is also a common index regarding human comfort maintaining a normal temperature.  Human comfort is ideally near 50% RH, while RD less than 30% is dry air and RD greater than 70% is considered humid.

When the air can't "hold" all the moisture,then it condenses as dew.

The formula for relative humidity is:

   rh = W/Ws


  • rh is the relative humidity converted to a percentage
  • W is the actual density of the vapor
  • Ws is the saturation density of the air.

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