1. What is Relative Humidity?

Relative humidity (RH) is the ratio of the current amount of water vapor in the air to the maximum amount that could be present at that temperature, expressed as a percentage. It's a key metric in meteorology, HVAC, and many industrial processes.

2. How Does the Calculator Work?

The calculator uses the relative humidity formula:

Where:

• \( RH \) — Relative humidity (percentage)
• \( e \) — Actual vapor pressure (kPa)
• \( e_s \) — Saturation vapor pressure (kPa)

Explanation: The formula compares the actual amount of water vapor in the air (e) to the maximum possible amount at that temperature (es), then converts this ratio to a percentage.

3. Importance of Humidity Calculation

Details: Accurate humidity measurement is essential for weather forecasting, indoor climate control, industrial processes, agricultural applications, and human comfort assessment.

4. Using the Calculator

Tips: Enter both vapor pressure values in kilopascals (kPa). Both values must be positive numbers, with actual vapor pressure (e) always less than or equal to saturation vapor pressure (es).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between absolute and relative humidity?
A: Absolute humidity measures total water vapor content (g/m³), while relative humidity measures how close the air is to saturation at its current temperature.

Q2: What are typical RH values?
A: Comfortable indoor RH is typically 30-50%. Below 30% may feel dry, above 60% can promote mold growth.

Q3: How does temperature affect RH?
A: Warmer air can hold more moisture, so RH changes with temperature even if absolute humidity remains constant.

Q4: How is vapor pressure measured?
A: Typically measured with psychrometers, hygrometers, or calculated from dew point temperature.

Q5: Why use kPa for vapor pressure?
A: kPa is the SI unit for pressure. 1 kPa = 10 hPa (hectopascals, commonly used in meteorology).