Enter the actual vapor density and the saturation vapor density into the calculator to determine the relative humidity.

Relative Humidity Formula

The following formula is used to calculate relative humidity. 

RH = VDa / VDs * 100
  • Where RH is the relative humidity (%)
  • VDa is the actual vapor density (g/m^3)
  • VDs is the saturation vapor density (g/m^3)

To calculate relative humidity, divide the actual vapor density by the saturation vapor density.

Relative Humidity Definition

The relative humidity is the ratio of the vapor density to the saturation density of water in the air.

Relative Humidity Example

How to calculate a relative humidity?

  1. First, determine the vapor density.

    Measure the water vapor density.

  2. Next, determine the saturation density.

    Measure the saturation water vapor density.

  3. Finally, calculate the relative humidity.

    Calculate the relative humidity using the formula above.

FAQ

What factors affect relative humidity?

Relative humidity can be affected by temperature, air pressure, and the presence of water vapor. As temperature increases, the capacity of air to hold water vapor increases, potentially lowering relative humidity if additional moisture is not added to the air.

How do you measure actual vapor density?

Actual vapor density can be measured using hygrometers, which often calculate it based on temperature and pressure measurements. Other methods include dew point measurements and direct chemical absorption techniques.

Why is understanding relative humidity important?

Understanding relative humidity is crucial for various applications, including weather forecasting, HVAC system design, and ensuring the comfort and health in indoor environments. It also plays a significant role in agriculture, determining the best conditions for plant growth and storage of agricultural products.