Absolute Humidity Calculator

The Absolute Humidity Calculator determines the actual amount of water vapor present in air, expressed in grams per cubic meter (g/m³). Unlike relative humidity, absolute humidity is independent of temperature and provides a direct measure of moisture content in air.

Modify the values and click the calculate button to use
Air Temperature °C
Relative Humidity %
Temperature Unit  
Atmospheric Pressure kPa

Related Relative Humidity Calculator | Dew Point Calculator | Mixing Ratio Calculator

Understanding Absolute Humidity

Absolute humidity is the mass of water vapor present in a unit volume of air, typically expressed in grams per cubic meter (g/m³). It provides a direct measurement of the actual amount of moisture in air, regardless of temperature.

Key Characteristics

Temperature Independence

Unlike relative humidity, absolute humidity does not change with temperature variations. This makes it particularly useful for:

Direct Measurement

Absolute humidity provides a direct measure of water vapor mass, making it ideal for:

Calculation Methods

From Temperature and Relative Humidity

Step 1: Calculate saturated vapor pressure using Magnus formula

Step 2: Calculate actual vapor pressure: e = (RH/100) × e_sat

Step 3: Apply ideal gas law: AH = (e × 1000) / (R_v × T)

Where R_v = 461.5 J/(kg·K) is the specific gas constant for water vapor

Applications

HVAC and Building Systems

Industrial Processes

Agricultural Applications

Typical Values

Condition Temperature RH Absolute Humidity
Desert Air 35°C 20% 7.1 g/m³
Comfortable Indoor 22°C 50% 9.7 g/m³
Tropical Climate 30°C 80% 24.3 g/m³
Saturated Air 25°C 100% 23.0 g/m³

Related Humidity Parameters

Specific Humidity

Mass of water vapor per unit mass of moist air (g/kg). Related to absolute humidity but accounts for air density changes.

Mixing Ratio

Mass of water vapor per unit mass of dry air (g/kg). Useful in meteorological applications.

Vapor Pressure

Partial pressure exerted by water vapor in air (kPa). Directly related to absolute humidity through the ideal gas law.

Measurement Considerations

Accuracy Factors

Calibration

Practical Applications

Process Control

Energy Calculations

Note: Absolute humidity calculations assume ideal gas behavior for water vapor, which is accurate for most practical applications at normal atmospheric conditions.