What is Relative Humidity?

Relative humidity (RH) is a measure of the current amount of water vapor in the air relative to the maximum amount of water vapor the air can hold at that same temperature. It is expressed as a percentage. Unlike absolute humidity, which measures the actual mass of water in the air, relative humidity is highly dependent on air temperature. Warm air can hold significantly more moisture than cold air, which is why 50% humidity on a summer day feels much more humid than 50% humidity on a cold winter day.

How to Use the Relative Humidity Calculator

Using this calculator is simple. To get an accurate reading, you need two pieces of data: the actual air temperature and the dew point temperature. Follow these steps:

• Select your preferred unit of measurement (Celsius or Fahrenheit).
• Enter the current dry-bulb temperature (the standard temperature read from a thermometer).
• Enter the dew point temperature (the temperature at which air must be cooled to become saturated with water vapor).
• Click "Calculate Humidity" to see the result.

Why Does Relative Humidity Matter?

Relative humidity plays a critical role in various aspects of our lives, including health, comfort, and industrial processes. When RH is too high, the human body struggles to cool itself through sweat evaporation, leading to heat exhaustion. In buildings, high humidity can cause mold growth and wood rot. Conversely, low humidity can lead to dry skin, respiratory irritation, and static electricity buildup. In fields like agriculture and HVAC engineering, maintaining optimal humidity levels is vital for crop yield and energy efficiency.

Frequently Asked Questions

What is the Magnus Formula?

Our calculator uses the Magnus-Tetens approximation, which is widely recognized for its accuracy in meteorological calculations. It relates saturation vapor pressure to temperature to derive the relative percentage of moisture present.

Can relative humidity exceed 100%?

In standard environmental conditions, relative humidity stops at 100%, which indicates the air is fully saturated and water will begin to condense into clouds or fog. However, in laboratory "supersaturated" conditions, it can technically exceed 100%.