Humidity Ratio Calculator

Humidity Ratio Equation:

\[ \text{Humidity Ratio} = \frac{0.622 \times \text{Vapor Pressure}}{\text{Atmospheric Pressure} - \text{Vapor Pressure}} \]

Humidity Ratio:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Humidity Ratio?

The Humidity Ratio (also known as mixing ratio) is the mass of water vapor per unit mass of dry air. It's a fundamental parameter in psychrometrics and HVAC calculations, representing the actual moisture content in air.

2. How Does the Calculator Work?

The calculator uses the Humidity Ratio equation:

\[ \text{Humidity Ratio} = \frac{0.622 \times \text{Vapor Pressure}}{\text{Atmospheric Pressure} - \text{Vapor Pressure}} \]

Where:

0.622 — Ratio of molecular weights of water vapor and dry air
Vapor Pressure — Partial pressure of water vapor in air (Pa)
Atmospheric Pressure — Total atmospheric pressure (Pa)

Explanation: The equation calculates the mass ratio of water vapor to dry air based on their partial pressures in the air mixture.

3. Importance of Humidity Ratio Calculation

Details: Humidity ratio is crucial for HVAC system design, moisture control in industrial processes, comfort analysis in buildings, and meteorological calculations. It helps determine dehumidification requirements and energy consumption.

4. Using the Calculator

Tips: Enter vapor pressure and atmospheric pressure in Pascals (Pa). Both values must be positive, and atmospheric pressure must be greater than vapor pressure for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: What units are used for humidity ratio?
A: Humidity ratio is typically expressed in kilograms of water vapor per kilogram of dry air (kg/kg).

Q2: How is vapor pressure different from relative humidity?
A: Vapor pressure is the actual partial pressure of water vapor, while relative humidity is the ratio of actual vapor pressure to saturation vapor pressure at the same temperature.

Q3: What is the constant 0.622 derived from?
A: 0.622 is the ratio of the molecular weight of water vapor (18.015 g/mol) to the molecular weight of dry air (28.965 g/mol).

Q4: Can this calculator be used for different pressure units?
A: The calculator requires inputs in Pascals. For other units (mmHg, inHg, bar), convert to Pascals first (1 mmHg = 133.322 Pa, 1 inHg = 3386.39 Pa, 1 bar = 100,000 Pa).

Q5: What are typical humidity ratio values?
A: At standard atmospheric pressure, humidity ratio typically ranges from 0.0001 kg/kg (very dry) to 0.03 kg/kg (very humid tropical conditions).