1. What is Relative Humidity?

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

2. How Does the Calculator Work?

The calculator uses the RH formula:

Where:

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

Explanation: The equation calculates what percentage the actual vapor pressure is of the saturation vapor pressure at the same temperature.

3. Importance of RH Calculation

Details: Relative humidity affects human comfort, building design, industrial processes, and is crucial for weather forecasting and climate studies.

4. Using the Calculator

Tips: Enter both vapor pressure values in kPa. Both values must be positive numbers, and the actual vapor pressure cannot exceed the saturation vapor pressure.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between RH and absolute humidity?
A: RH is relative to temperature (percentage), while absolute humidity measures the actual water content (g/m³) regardless of temperature.

Q2: What are comfortable RH levels for humans?
A: Typically 30-60%. Below 30% can cause dryness, above 60% promotes mold growth and feels uncomfortable.

Q3: How does temperature affect RH?
A: Warmer air can hold more moisture, so RH changes with temperature even if the actual water content stays the same.

Q4: How is saturation vapor pressure determined?
A: It's calculated from temperature using the Clausius-Clapeyron equation or looked up in thermodynamic tables.

Q5: Why use kPa for vapor pressure?
A: kPa is the SI unit for pressure. Some systems may use hPa (1 hPa = 0.1 kPa) or mmHg (1 kPa ≈ 7.5 mmHg).