Relative humidity Calculator

1. Definition

Relative Humidity (RH) is the ratio of the actual amount of water vapor in the air to the maximum amount the air can hold at the same temperature. It is expressed as a percentage.

2. Background Theory

RH is defined as:

Where:

• Pw = actual vapor pressure (from dew point)

• Pws = saturation vapor pressure at dry-bulb temperature

The calculator uses the Magnus formula:

This is widely used for HVAC psychrometric calculations.

3. How the Calculator Works

1. User inputs:

   • Dry-bulb temperature (°C)

   • Dew point temperature (°C)

2. Magnus equation is used to compute:

   • Saturation vapor pressure at dry-bulb temperature

   • Actual vapor pressure from dew point

3. RH is computed as the equation stated earlier

4. The calculator outputs relative humidity in %.

Even though this calculator provides a fast way to determine relative humidity from dry-bulb and dew point temperatures, real HVAC spaces behave far more dynamically. Air mixing, diffuser performance, heat gains, occupant activity, and ventilation patterns all influence the actual humidity distribution in a room. For engineers who need to visualize how humidity interacts with airflow, temperature, and ventilation inside real spaces, tensorHVAC-Pro offers an intuitive HVAC-focused simulation environment that makes it possible to analyze real performance without needing CFD expertise.