1. What is Relative Humidity?

Relative Humidity (RH) is the ratio of the current absolute humidity to the highest possible absolute humidity at that temperature, expressed as a percentage. It indicates how much water vapor is in the air compared to how much it could hold at that temperature.

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 amount the air can hold at that temperature (es), then converts this ratio to a percentage.

3. Importance of RH Calculation

Details: Relative humidity affects human comfort, building design, industrial processes, and weather forecasting. It's crucial for HVAC systems, agriculture, and many manufacturing processes.

4. Using the Calculator

Tips: Enter both actual vapor pressure and saturation vapor pressure in kPa (kilopascals). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between absolute and relative humidity?
A: Absolute humidity measures actual water vapor content (g/m³), while relative humidity measures this as a percentage of maximum possible at that temperature.

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

Q3: How does temperature affect RH?
A: Warmer air can hold more moisture, so RH decreases as temperature rises (if moisture content stays constant).

Q4: How is saturation vapor pressure determined?
A: It's calculated from temperature using the Magnus formula or similar equations.

Q5: Why measure in kPa?
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).