Mixing Ratio of Air Calculator
Calculate water vapor mixing ratio, saturation ratio, and relative humidity for atmospheric analysis
Calculate Mixing Ratio
Ambient air temperature for calculation
Temperature at which air becomes saturated
Local atmospheric pressure at measurement location
Mixing Ratios
Humidity Analysis
Very humid - near saturation, possible condensation
Calculation Formulas
Vapor Pressure: e = 6.11 × 10^(7.5 × T_dew / (237.7 + T_dew))
Mixing Ratio: w = 621.97 × e / (p - e)
Relative Humidity: RH = (w / w_s) × 100%
Input Values: Air: 27.0°C, Dew: 25.5°C, Pressure: 1013.3 hPa
Humidity Comfort Scale
Example Calculation
Meteorological Conditions
Location: San Antonio, Texas (Summer Day)
Air Temperature: 27.2°C (81°F)
Dew Point: 25.6°C (78°F)
Station Pressure: 1006 hPa
Step-by-Step Calculation
1. Vapor Pressure: e = 6.11 × 10^(7.5 × 25.6 / (237.7 + 25.6)) = 32.4 hPa
2. Saturation Vapor Pressure: es = 6.11 × 10^(7.5 × 27.2 / (237.7 + 27.2)) = 36.0 hPa
3. Mixing Ratio: w = 621.97 × 32.4 / (1006 - 32.4) = 20.7 g/kg
4. Saturation Mixing Ratio: ws = 621.97 × 36.0 / (1006 - 36.0) = 23.1 g/kg
5. Relative Humidity: RH = (20.7 / 23.1) × 100% = 89.6%
Result: High humidity, feels sticky and uncomfortable
Mixing Ratio Values
Typical Ranges
Arid climates: 2-8 g/kg
Temperate: 8-15 g/kg
Tropical: 15-25 g/kg
Extreme humid: 25+ g/kg
Units
g/kg (grams per kilogram)
kg/kg (mass fraction)
ppmv (parts per million)
Key Constants
621.97 (molecular weight ratio)
6.11 hPa (reference pressure)
237.7°C (Magnus constant)
Applications
Weather forecasting & meteorology
HVAC system design & control
Indoor air quality assessment
Aviation weather analysis
Agricultural planning
Humidity Types
Mixing Ratio
Mass of water vapor per mass of dry air (conservative property)
Specific Humidity
Mass of water vapor per total mass of moist air
Relative Humidity
Percentage of saturation at current temperature
Absolute Humidity
Mass of water vapor per unit volume of air
Understanding Mixing Ratio
What is Mixing Ratio?
Mixing ratio is the mass of water vapor per unit mass of dry air, expressed in grams per kilogram (g/kg). Unlike relative humidity, mixing ratio is a conservative property that doesn't change with temperature alone.
Why Use Mixing Ratio?
- •Conservative property - doesn't change with temperature
- •Better for tracking air masses in meteorology
- •More sensitive than relative humidity for dry conditions
- •Essential for atmospheric thermodynamics
Saturation Mixing Ratio
The saturation mixing ratio represents the maximum amount of water vapor that air can hold at a given temperature and pressure before condensation occurs.
Applications
- •Weather forecasting and storm tracking
- •HVAC system design and operation
- •Agricultural moisture management
- •Building envelope performance analysis
Magnus Formula for Vapor Pressure
e = 6.11 × 10^(7.5 × T / (237.7 + T))
w = 621.97 × e / (p - e)
Where T is temperature in °C, p is pressure in hPa
• 6.11 hPa (reference vapor pressure)
• 621.97 (ratio of molecular weights)
• 237.7°C (Magnus constant)
• Desert: 2-5 g/kg
• Temperate: 8-12 g/kg
• Tropical: 15-22 g/kg
• Specific humidity ≈ w/(1+w/1000)
• Relative humidity = w/ws × 100%
• Virtual temperature calculation